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About Google Book Search Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web at|http: //books .google .com/I PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC. VOLUME XIX. 1907. SAN FRANCISCO: PRINTED FOR THE SOCIETY. 1907. I • ■ Aim ■ •. - 1 \ 1 X I f /AMD j ■ 0*.5 I * A PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XIX. San Francisco, California, February 10, 1907. No. 112 LIST OF MEMBERS OP THE ASTRONOMICAL SOCIETY OF THE PACIFIC. January, i, 1907. OFFICERS OF THE SOCIETY. Mr. A. O. Levschner President Mr. Chas. S. Ci'shinc First Vice-President Mr. A. H. Babcock Second Vice-President Mr. W. W. Campbell Third Vice-President Mr. R. G. .\iTKEN > - ., ^ n ~ V Secretartes Mr. F. R. Zir.L j Mr, F. R. Zi EL Treasurer Board of Directors — Messrs. Aitken, Babcock, Burckhaltbk. Campbell, Ckockek. CusHiNO. Hale, Leuschner, Richardson, Spreckels, Ziel. Finance Cotnmittcc — Messrs. Cushikg,. Crocker, Richardson. Committee on Publication — Messrs. Aitken, Townlev, New kirk. Library Committee — Mr. voM Geldern, Mr. Richardson, Mrs. Schild. Committee on the Comet-Medal — Messrs. Campbell (ex-officio), Burckhai.ter. Pehrixe. BRUCE MEDALISTS. Prof. Simon Xewcomb 1620 P St., Washington, D. C. Prof. Arthir Auwers { ^'g^^i;,^';; "'' ^- '^- ^"""' c- TA /- , , / Athenaeum Club, Pall Mall, Sir Davh. Gill \ London. England. Prof. G. V. SCHL.PARELLI { R•J,Oss;:r^•atorio di Brera. Milan. Sir VV.LLI..M Hoggins { ^England.^"''" "'"' ^"'^''"' Prof. HHRM..X. Carl Voc«. { AfJ^niltotS Ge?^^ar- PATRONS OF THE SOCIETY. Dr. Edward Singleton Holden West Point, N. Y. Joseph A. DoNOHOE.t Alexander MoNTCOMERY.f Catherine Wolfe Bruce.! John Dolbeer.! William ALVORD.f William Montgomery PiERSON.f t Deceased. * » Publications of the MEMBERS OF THE SOCIETY.* Prof. R. G. AiTKEN { ^'nfo?cir'°'''' ^^°""' "''''"' Dr. Sebastian Albrecht { ^'f,l^on,'"cir''''^'' ^*°""' "^"" Prof. W. Steadman Alois,* f.r.a.s.. { Old^Headington, O.xford. Eng- Prof. W. D. Alexander { "^""{".iJ^^^; Honolulu. Hawaiian Mr. Richard H. Allen* Chatham, Morris Co.. X. J. Miss Edith W. Allyne { ^^j^"*'' ^'- ^■''" ^'^''^'''^''- ,, f.„ „ A.— „,.,. / Lazard Freres & Co.. lo Wall Mr. Charles Altschul [ gj^ ^^^ Y^^^ ,^, Y Dr. G. DEL AMD {4 Co-J^J;: ^e Ara.ula, Madri {'n"" "" ^'' ''"' ^°* Mr J. C. Ceb.ian> { ^%' »'?<' O^"™ S..,- S.n I Iranciaco. Cal. Mr. A. J. Ckaupihux { SludenU'^ Obstrvatory. Berke- Mr. H. C. CHEsmouoH ( 254 Calijornia Si., San Fra. I. CISCO, Cal. Mr. Mateo Clabk* { " ?on" in^anl^" ^ ^" ^" Mr. E. F. CoDDiNGTON jg W. nth Ave., Columbus, O. Mr. A. L. CoLTOK* Box 1 148 Madison, Wisconsin. {Care Bedford Petroleum Cic, 67 Boulevard Haiissmann, Paris, France. Mr. Fr.^nk V. CoRN-ise { ^'°^^^"^^^| ^^^^- ^='" '""'''"' Mr J Costa ( 104 Montgomery St., San Fran- Prot. Russell Tracv Crawford ( Stndents' Observatory. Berke- I ley, Cal. Mr. Gecirce Crocker* Mills Bldg., New York, N. Y. Mr. He.xrv J. Crocker { ^^Lo'^Sr ^'" ^''" ''""' Mr. William H. Crocker* { ^^S^js^'J'' aT' ^*"''' ^^" Miss S. J. Cunningham {33^^ Arch ' St.. Philadelphia. Prof. Heber D, Curtis Casilla I2ig, Santiago, Chile. OTarre CO, Cal. ■M.,.Ew,»D,v,.„.. f*H„Sr'- ""-■ °'""''' Mr. E. A. Demcke 1604 Scenic .\ve., Berkeley, Cal. Mrs. John H. Devebeuk { ^Ohio^'"'"*' ^'"'*' *^'*"'^"'*' Mr. Geo. L. Dillman. c.e. 917 Grand St.. Alameda, Cal. jjWarwickRond, Earl's " S. W London, Eng. Mr. Edward "'ttoNOHo'E?*.?."' [ Ho. 10 hoe- Kelly Banking Co., I ann rrancsco. Ual. {VJce-Presirlent Donohoe-Kelly Banking Co., San Francisco, Cal. Mrs, An.va Palmer Draper* { ^7^i^a', Berke- ley, Cal. 2449 Webster St., Berkeley, Cal. 808 Juniper St., San Diego, Cal. Conant Hall, Harvard Univer- sity, Cambridge, Mass. Formerly X. E. cor. Bush and Sansome Sts.. San Francisco, Cal. 1652 O'Farrell St., San Fran- cisco, Cal. London, Paris & American Bank, San Francisco, Cal. 3 Duntrune Terrace, Broughty Ferry, Dundee, Scotland. 722 Monadnock Bldg., San Francisco, Cal. Mechanics' Savings Bank, 143 Montgomery St.. San Fran- cisco, Cal. 308 California St.. San Fran- cisco, Cal. Director of the Solar Observa- tory, Solar Observatory Of- fice, Pasadena, Cal. 140 Broad St., New York, N. Y. Porter Building, San Jose, Cal. 1414 Post St., San Francisco, Cal. ^Astronomical Society of the Pacific. 5 Mr. Andrew P. Heskel { ^'^j,io^'''"' ^' ' ^'"'■""'"'' n ^ u . . i Director of the Observatory, Rev. G. HE.mA. ,., \ p^^,,,, „„;„ Mr. HcAO; L. H.ti,' { '""S'lVo^^cS""'"' ^'" ^"' Mi., A,>.iA„,. M. Ho.»: { LickObgvator,-, Mot.ol H.m- Mr. S.Mt.-«. V. Ho™.>^•,■ r...».s... { 9.jM.ii«>n .W._ Morri.lowo, °'- ^-"j^^s^-i.. { "^"TZ '■'""°"' ""•' Mr.JoHKD.H„o.„ {n„Sar"" "■■ "^ Ho,, c. w™ Ho..«.' { ''•f,i;"c°;r """■ ^" "'"" Mr. JoH» L. How.m, j «J.^f ''""■' ^' ' ^" F™"'"' Mr. Wm. How.,,. { «Vi "™"" ^'- "'"""'"• Prof. Chas. S. Howe j C.K .^Ob.ervatory. Oevehnd. Prof VV T Hii.«v J Director Detroit Observatory. Prof. W. J. HussEV j ^^^ ^^^^^ Micltigan. Mr, EowAao laviN,-. I iS30 Shattuck Ave., Berkeie,, I Cal. Mr. F.AKK jAV«s I\ U..Telegr.pi. Co., San \ Irancisco, Cal. Mr. C.i..«LBS C. Keenev* f ^a^? Cby St., San Francisco, \ Cal. ,,,_,. ( Hibernia Savings and Loan Mr. J.vMEs R. Kelly j Society. San Francisco, Cal. ( Division of Engineering. Har- Prof A. E. Kemselly* F.B..VS J vard University. Cambridge, ( Mass. Mr. ToK\ALD Kohl' Odder, Denmark, -, _ ,. I Schone Aussicht 20. Wiesba- Mr. Fk. KoEPPEN ^ ,|^.„ Germany. Prof. H. Krevtz Kiel, Germany I P O. Box Pachiica. State Mr. C. F. DE Lasdero' .{ j-jidaig^. Mexico. Mr. O. V. La-vce 1400 Milvia St., Berkeley, Cal. „ , ^ , , r Director Mount Lowe Ohser- Prof. Eog.-lr L, L.*HK1N \ vatory. Echo Mountain, Cal. ,, ,, , f Casa de Moneda. City of Hon. Makuel I-ernandez Le.\l ^ Mexico, Mexico. „ _ , „ , I Protea. Rcig.ite. Surrey. ling- Rev. Prof. E. Ledger, m.a., f.r.a.s — ^ j^^^j D t 4 n t = / Direclor Students' Observa- Prof. A. O. Lelschner \ ,^y Berkeley C;i1, ,, ^ „ I - ) Care Wm. Salomon & Co., as Mr. Clarence Macke.vzie Lewis'... \ ^ j,^^^^ g, u^„ v^rk. N. Y. ,, . , ( 6to Commercial St., San Fran- Mr. Adolph Lietz \ ^-^^^ Cal. 6 Publications of the Mr. John D. Locke Haverhill, New Hampshire. Mr. Henry B. Loomis* Seattle, Washington. Mr. W. H. LowDEN { ^'tiS'Sl'^ ^*' ^"^ ^""' Mr. EtiWARii G. Li-KENS ijfe Jackson St., Oakland, Cal. Hon. Geo. Rlssell Lukeks 1350 MadiM>n St., Oakland. Cal. .,,-,71 / Care R. G. Lnnt, Los .Xngeles, Mr, I-R.^NK E. LUNT 1 Tal s • Mr. WauAM A. Macee { ^ ^5',°;;*'^*"'' ^'■- ^'" ''""" Mr, Mar.si.en Manson. c.f.., pb....,,. { ^'^^^""^^ ^' ' ^'" I^^n^^^^". M F \I BTFN'i i Collegepoint, Queens Co.. New {Puritatanga, Marlinborongh, Wairarapa, Wellington, New Zealand. Mr. W. H. M«w,. ,..,.. { '"LSn'S'EK/*"*"*"' M... M.., C. MCO.M.S { ■''>s™g.'„ iT^^.jf^-Sr"' Mr. G.™i, W. McEHDNiv { "IJ^^!"^, ■"*■ ^" ^"'- Prot. T. E. McK,NK., | "'Si'i^o.Yr"*' "'"'" Prof. Malcolm McNeill. Lake Forest, III. Mr, J, Walter Miles Irwin, Pa. Prof. E. Miito, f Uni,.r.ii, of Kan.a.. L..- I rence, Kansas. Hon. D. O. Mills* 15 Broa.l St.. NVw York. N. Y Mr. James K, Moffitt { ^'"^nckm^Cal ^^"*'' ^'"' Mr, E, J. MoLERA,* CE, I ^f^^^^JT'^"*** ^'■' ^^" '"""'' Mr. W. H- S. MoNCK, f.ka. Dr. J. H. Moore { ^'nl'on ''caT'""'' """"' """" Mr. Fremont Morse, u.s.c. * csirvkv | P>9i ^""^ ^^''' ^"^ F"ncisco. Mr. C, A, Ml'riiock Hon. n, D. Mlrphy* J 2393 Filbert St„ San Fi ■ 1 Cal, I Formerly 530 California St, ■ \ San Franci.sco, Cal, \t>- rii.D.Tc Vc. .^u I '44 Stenart Sl„ San Francisco Mr, LIHRLES NELSON j ^^j Mr H F Xfwml«fr\«i / Olisenalory of the L'uivcr ■ sily, Cambridge. Englar' I Lick Observatory. Moimt Hai I tlton, Cal. Mr. P. NooRDHOFF Grocningen. Holland. Dr. B. L. Xeivkirk.. P. Noordhoff.. . i Rose O'Hallora.v I 726 Ashbury St.. San Fr; Astronomical Society of the Pacific. 7 Mr. George Frederick Paddock Casilla 1219, Santiago, Chile. Hon. George C. Pardee Oakland, Cal. Mr. John Patten* { ^N. Y. ^^''' ^*' ^^^ ^'"^' Hon. Geo. C. Perkins* Oakland, Cal. Prof. C. D. Perrine { ^So^t^T"'''''' ^°""' """"' Hon. James D. Phelan { '^'^rUSo. Si' ^''^•• Mr. Henrv Phipps. Jr.* { '^^buX'Pa!'''"" * ^''" ^'"" Mr. Lawrence H. Pierson { ^^g^^ ^'""^ *^°- S^" ^"""sco. Mr. Ruthven W. Pike* { ^"fLoif ''"*" ^^^- ^*''"«°' Miss Juliet Porter* ^7 Deane St., Worcester, Mass. Mr. Charles A. Post, f.r.a.s Bayport, Long Island, N. Y. Mr. Walter A. Post, f.r.a.s Newport News, Virginia. Mr. Enos Putm an* Grand Rapids, Michigan. Mr. Carl Ramus (A"'' Surgeon U. S.. Marine t Hospital, San Francisco, Cal. Rev. J. L. RiCARD. S.J Santa Clara, Cal. Mr. Daniel S. Richardson { ^^^sVoTkL^^^^^ '^^-^ Mr. George W. Ritchey ( ^''IZ^^rT^''^ ^^^""^ ^'''' Forei^ Assoc, e.a.8. I ^^ena, Cal. {Chateau Rosa Bonheur. By Thomery, Seine et Marne, France. r Formerly of Leavenworth and Mrs. Arthur Rodgers*.. .t < Vallejo Sts., San Francisco, 1 Cal. Dr. W. H. Rollins 250 Marlboro St., Boston, Mass. The Earl of Rosse, f.h.a.s / ^»r ^^^^^^^ Parsonstown, Ire- 1 land. Baron Albert von Rothschild* Vienna, Austria. Mr. W. P. Russell ( Pomona College, Claremont, ' Cal. Mr. E. J. DE S.ABLA, Jr.* I ^9i6 Octavia St., San Fran- l CISCO, Cal. Mr. John W. Salsbury Port Tampa City, Florida. Prof. J. M. Schaeberle* ( 502 Second St., Ann Arbor. I Mich. Mr. Jacx)B H. Schiff* [ 93^, ^^^^ A^'«' ^'^^ York, I N. Y. Mrs. E. T. ScHiLD. p9o8 Broadway, San Francisco. I Cal. Mr. Herman Schussler | Pacific-Union Club, San Fran- l CISCO, Cal. Mr. James L. Scott, f.r.a.s ( ^^^t Scot;, Harding & Co.. I Shanghai, China. Prof. Frederick H. Seares ( ^'JS''^''^ . H^J^ Observatory, I Columbia, Mo. Rev. George M. Searle, cs.p | ^t- Paul's Church 41S W. 59th I. St., New York, N. \. 8 Publications of the Dr. T. J. J. See* ( ^^''^} Obsen'atory, Mare Isl- l and, Cal. Mr. Charles S. Smith* | -5 % 47th St., New York, Mr. Elliott Smith / Cincinnati Observatory, Sta- l tion O, Cincinnati, Ohio. Mr. E. C Smith* Saint Albans, Vermont. Mr. Sommers N. Smith < ' The Neafie & Levy Ship and Engine Building Co., Phila- delphia, Pa. Mr. Wm. H. Smyth Fernwald, Berkeley, Cal. Prof. M. B. Snyder / director of Philadelphia Ob- \ servatory, Philadelphia, Pa. Mr. George W. Spencer / ^M. California St., San Fran- \ Cisco, Cal. Mr. A. B. Spreckels* | '^^q^^^^ ^^^ ^^" Francisco, Mr. C A. Spreckels* San Mateo, Cal. Mrs. C. A. Spreckels* San Mateo, Cal. Mr. Rudolph Spreckels | ^oro Gough St., San Francisco, Miss Gertrude Stanford | ^"^'^^ Springs, Alameda Co., Mr. Thos. W. Stanford* i ^'♦f,. ^"fsell St.. Melbourne, \ Victoria. Mr. C. M. St. John [ ^\, ^- . Custom House. San \ Francisco, Cal. Mr. Julius Stone* [^^^''l^}^ Ohio Central Fuel \ Co., Columbus, Ohio. Mr. V. Stroyberg* [ Observatory, Copenhagen. Den- \ mark. Mr. Daniel Suter | ^^Caf"'^ ^^"^ ^^" ^^^"^cisco. Mr. C. F. A. Talbot { ^^Pj ^^'^ ^^53, San Francisco, Mrs. Louis Taussig / ^^^7 California St., San Fran- \ Cisco, Lai. Dr. Otto Tetens \ ^"y^'' Observatory, Kiel, Ger- \ many. Dr ToHv M Thomf* i National Observatory, Cordo- ur. JOHN M. 1 HOMh ^ ^^ Argentine Republic. Dr. S. D. TowNLEV | ^^^'^^^ Observatory, Ukiah. 1 Lai. ur. A. b. 1 lchler I ^yj.^ gj^ 5^j^ Francisco, Cal. Prof. R. H. Tucker { ^\'uoS^c^^^^^ ^^""' "'''"' Dr. Arthur B. Turner Montclair, N. J. Mr. Henry J. Turner* \ ^^^^^S'. ^='PP='''='""°*='' ^''•' Major Omar A. Turney Box 396, Phoenix, .Vrizona. \f.. i^ T XxrcrAXT* f Seaboard Bank, 24 Market St., Mr. K. J. Tyson ^ 5^^ Francisco, Cal. Astronomical Society of the Pacific. g ,, ~ ,. f Director National Observa- Mr. Felipe Valle [ j^^_ Tacubaya, Mexico. Mr. Edward H. Van- Incen [^ ^Y. '"' ^' ' ^''" ^*'"'' Mr. F. W, Van SiCKLEN { '^^L^"'"' '''"'"■■ ^'^'"'''^' „ ,., ,, ( Care of Carl Zeiss; z. Hd. Dr. Dr. W. ViLLicER I ^(^p„ R„hr, Jena, Germany. {Care of Warner & Swasey, F^st Prospect St., Cleveland, Ohio. Dr. \V. Seward Webb T. . . . 51 E. 44th St.. Xew York, N. V. Mrs, W. Seward Webb 680 5th Ave. New York. N. Y. n , r, I iir i Imperial Ohscrviilory Prague, Prof. Dr. L. Weinek ( A u.iro- Hungary. Mr. C A. G, Wevmouth 2325 Blake St., Berkeley, Cal. Dr. Andrew D- White* Ithaca, N. Y. ., T- .r iir f JOO West Park .\ve., Valley Mrs. Elsie Hadley White | -'^.,,, j^.^„,, Dakota. Mrs. Marv R WtLLKARTH* | 2.2 ^Michigan .\ve., Chicago, ^ , , „ ,., . f Si. Petersburg, W. O. 9"! 'in*> Colonel B. Witkovskv* { ^ ^_ R„,^ia *' ,, u Hf 7 . / "818 California St.. San Fran- Mr. Frederick W. Zeile* < ^^^^^ Q^^ „,,-,,, / Smichow Pragtic, Bohemia. Prof. C. V. Zencer. f.b..v.s { A„^tro-HiinEary, \(, p c 7... J S<* Franklin St., San Francis- Mr.F.R.ZiEL I ^^ f-^,^ INSTITUTION A L MEMBERS. T- ,. n i Williams College, Willianis- FiELD Memorial Obser\'atorv -j \^^„ j^i^^s i.,r-=, , n...™. «,».. / University of St. Petersburg, Imperial Observatory | ^^^^.^f Taschkent, Turkestan, Russia California State Library Sacramento, Cal. LiBR.\RY OP THE Chabot Observatory Oakland, Cal. Free Public Library Worcester. Mass. The John Cbeb.vs Lihh.vicv Chicago, 111. „.„S,T^ " ;^"; ) Stanford University. Cal. LlBBABV OF THE LeLAND StaNI University Library of the Lick Observatory. . . Mount Hamihon. Cal. , ., ,, (go Grove St., San Francisco, Library OF the Mechanics Institute < Cal Library or ike Minneapolis Athe- 1 Minneapolis, Minn, ..,,-,, (40 Ufayette Place. New York. New \ork Public Library 1 N Y " Oakland Free Public Library Oakland, Cal. Library op Princeton University Princeton. N. J. The Public Library Boston. Mass. lO Publications of the Library of St. Ignatius College.... { ^Cal"^^^' ^^" ^^" ^^^"^^s^^' SwARTHMORE CoLLEGE LiBRARY Swarthmorc, Pa. Library of the U. S. Military \ ,,r . r» • .^ xt vr Academy [ West Point, N. \. Library of the Unutrsity of Cali- fornia Library of the University of Illi- nois ^"' mAL'*^. ."^ .^:*."'™""'. °^. .'.!"; } Bloomington, Indiana. ^'°Vm•^m7.^^'.'!'.T.'"^°^^'.'!!'■ } Philadelphia. Pa. Library of the University of Sofia. Sofia, Bulgaria, Europe. Wellesley College Library Wellesley, Mass. Library of Yale University New Haven, Conn. Lowell Observatory Flagstaff, Ariz. Shattuck Observatory { ^^'"^^^^ ^•'"'«''' H^""^"' > Berkeley, Cal. > University Station, Urbana, 111. CORRESPONDING INSTITUTIONS. Albany, New York, Dudley Obser\'atory. Allegheny, Pennsylvania, Allegheny Observatory. Armagh. Ireland, Armagh Observatory. Berlin, Gennany, Konigl. Astronomisches Recheninstitut. Berlin, Germany, Konigliche Sternwarte. Brussels, Belgium, Bibliotheque de la Societe Beige d'Astronomie, 27 Montague de la Cour. Brussels, Belgium, Observatoire Royal de Belgique. Cambridge, England, University Observatory. Cambridge, Massachusetts, Harvard College Observatory. Cape Town, Africa, Royal Observatory. Catania, Italy, Societa degli Spettroscopisti Italiani. Christiania, Xorway, Universitats-Sternwarte. Cincinnati, Ohio, Cincinnati Observatory, Station O. Columbia. Missouri, Laws Observatory, University of Missouri. Cordoba, Argentine Republic. National Observatory. Dorpat, Russia, L'nivcrsity Observatory. Dublin, Ireland. Dunsink Observatory. Dublin. Ireland, Royal Dublin Society. Edinburgh. Scotland, Royal Observatory. Geneva, Switzerland. Observatoire. Glasgow, Scotland, University Observatory. Gotha. Germany, Grossherzogliche Sternwarte. Goettingen. Germany, Konigliche Sternwarte. Greenwich, England, Royal Observatory. Hamburg, Germany, Hamburger Sternwarte. Heidelberg, Germany, Astrometrischc Abteilung der Grosshcrzoglichen Sternwarte. Astronomical Society of the Pacific. 1 1 Heidelberg, Germany, Astrophysikalische Abteiliing der Grossherzog- lichen Sternwarte. Helsingfors, Russia, University Observatory. Hiram, Ohio, Observatory of Hiram College. Kasan. Russia, University Astronomical Observatory. Kiel, Germany, Universitats-Sternvvarte. Kodaikanal, Palani Hills, South India, Observatory. Koenigsberg, in Pr. Germany, Konigliche Sternwarte. La Plata, Argentine Republic, Observatory. Leipsic, Germany. Universitats- Sternwarte. Leyden, Holland, Universitats-Sternwarte. Lisbon (Tapada), Portugal, Real Obser\'atorio. London, England, British Astronomical Association, care of F. W. Levander, 30 North Villas, Camden Square, N. W. London, England, British Museum. London, England, Royal Astronomical Society. London, England, 3 Venilam Bldgs., Gray's Inn, The Nautical Almanac. Lund, Sweden, University Observatory. Madison, Wisconsin, Washburn Observatory. Madrid, Spain, Observatorio Astronomico. Marseilles, France, Observatoire. Melbourne, Victoria, Observatory. Mexico, Mexico, Sociedad CientiBca "Antonio Alzate." Milan, Italy, Osservatorio Astronomico di Brera. Moscow. Russia, University Observatory. Mount Wilson, via Pasadena, Cal., Solar Observatory. Munich, Germany, Konigliche Sternwarte. Naples, Italy, Osservatorio Astronomico. New Haven, Connecticut, Yale University Observatory. New York, New York, American Mathematical Society. New York, New York, Columbia University Observatory. Nice, France, Observatoire. Northfield, Minnesota, Goodsell Observatory. Oxford, England, Radcliffe Observatory. Oxford, England, University Observatory. Padua. Italy, Osservatorio Astronomico. Paris, France, Bureau des Longitudes. Paris, France. Observatoire National. Paris, France, Rue Cassini 16, Societe Astronomique de France. Philadelphia, Pa., 105 South Fifth St., American Philosophical Society. Potsdam, Germany, Astrophysikalisches Obser\'atoriuni. Prague, Austro-Hungary, Universitats-Sternwarte. Pulkowa, Russia, Imperial Observatory. Rio de Janeiro, Brazil, Observatory. Rome, Italy, Osservatorio Astronomico del Collegio Romano. Rome, Italy, Specula Vaticana. San Francisco, California Academy of Sciences. San Francisco, California, Technical Society of the Pacific Coast. Stockholm, Sweden, University Observatory. 12 Publications of the Strassbnrg, Germany, Universitats-Sternwarte. Sydney, Xew South Wales, Observatory. Tacubaya, Mexico, Observatorio Astronomico Xacional. Tokio, Japan. University Observatory. Toronto. Canada, Astronomical and Physical Society of Toronto. Toulouse, France, Observatoire. Turin, Italy, Osservatorio Astronomico. University Park, Colorado, Chambcrlin Observatory. University of Virginia, Virginia, McCormick Observatory. Upsala, Sweden, University Obser\'atory. Vienna, Austria, K. K. Sternwarte. Vienna (Ottakring), Austria, Von Kuffnersche Sternwarte. Washington, District of Columbia, Library of Congress, Periodical Division. Washington, District of Columbia, National Academy of Sciences. Washington, District of Columbia, Naval Observatory. Washington, District of Columbia, Smithsonian Institution. Washington, District of Columbia, The American Ephemeris. Washington, District of Columbia, U. S. Coast and Geodetic Survey. Williams Bay, Wisconsin, Yerkes Observatory. Zurich, Switzerland, Observatory. EXCHANGES. Astro physical Journal, Williams Bay, Wisconsin. Popular Astronomy, Northfield, Minn. Prof. Dr. H. J. Klein, Editor of Sir ins, Theresien St. 85, Koln- Lindenthal, Germany. The Observatory, Greenwich, England. FOR REVIEW. [Sec Publications A. S. P., Vol. VIII, p. 101.] The Call, San Francisco, California. The Chronicle, San Francisco, California. The Examiner, San Francisco, California. 7^ he Mercury, San Jose, California. The Record-Union, Sacramento, California. The Times, Los Angeles, California. The Tribune, Oakland, California. ' Astronomical Society of fhe Pacific. 13 METHODS OF MEASUREMENT AND REDUCTION OF SPECTROGRAMS FOR THE DETERMINA- TION OF RADIAL VELOCITIES. Bv J. H. MookE. There is probably no field of astronomy in which the devel- opment of instruments and methods has been so rapid as in the application of the spectroscope to the detennination of the radial velocities of stars according to the Doppler-Fizeau prin- ciple. In the first investigations made by Huggins in 1867, and by Vogel in 1872, the observations were visual, and it was not unusual to obtain discrepancies in the results amounting to as much as the quantities to be measured. Observations of value date from the application, by Vogel in 1887, of the photographic method to this problem, a method which had already achieved remarkable results in the hands of Professor PicKERiN't; in his qualitative studies of stellar sf)ectra. Follow- ing this and the subsequent improvement in design of spectro- graphs and methods of reducdon in wliich Professor C.\mp- BELL at the Lick Observatory led the way, there has been a continual development in the instrumental and observational side giving si)ectrogranis of greater accuracy. At the same time refinements have been introduced into the methods of measuring and reducing these spectrograms in order to obtain from them velocities as accurate as the plates will warrant. It will be the purpose of the present article to outline the various methods which have been used for the measurement and reduction of spectrograms for radial velocity '" "" ""' "'""'" ""■'" * "" given the wave-lengths of the lines I : of the Sun taken from Rowla.\d's 435".".i" '3433 304 Prehminary Table of .Solar Wave- ', '- '. Lengths. The second colnmn con- 4Soi.448 41,72? 1^7 '3'f^ ^^^ micrometer reaiiings cor- rcspniiding to the wave-lengths of the first column. These settings 4f>$(i.f^44 C;<).215 434 are computed from the constants of the Sun plate. The third column contains the values of rl], the factor for each line by which the displacement is multiplied in order to obtain the corresponding velocity in kilometers per second; 1'], the velocity in kilometers per second corresponding Astronomical Society of the Pacific. to a displacement of one tenth-meter velocity of light wave-length ^ — . The quantity r, the number of tenth-meters in one revolution of the screw, is obtained from the original con- stants of the dispersion formula. Its value will be deduced later. In measuring the star plate, set it so that one of the compari- son lines — say 4338.084— has the tabular micrometer reading 10.258, and make the settings on the other comparison and star lines as described above. Take the difference, micrometer reading of comparison line on star plate minus micrometer reading of same comparison line in our table (under Sun). Next plot a curve with wave-lengths as abscissas, and these differences as ordinates. Construct a table of micrometer set- tings ( for zero velocity) for star lines measured on the plate by applying to the tabulated settings for these lines corrections read off from the curve. Suppose, for example, we wish to obtain the reading for the line 4351.930 on a star plate (1. e. the reading which this star line would have if unshifted by radial velocity). We read off from the curve the difference corre- spowling tn A 4351.930 and add it to the micrometer reading 13.433 '" ^^^ table. Suppose it is -j- .022. Then the reading for zero velocity would be 13.455. and if the micrometer set- ting of this line on the star plate is 13.330, then tlie displacement is — .135. Where there are comparison lines corresponding to star tines some observers take the difference between the micrometer readings directly for the displacements, while others rigorou--'ly follow the process just outlined. Having now the displacements for each of the stellar lines measured it is neces- sary to multiply each one by the corresponding r]] in order to obtain the velocity. The mean of the velocities obtained from the different lines, which we may call r,, is the relative velocity of the star and observer in the line of sight. It is necessary to apply two small corrections to v^ ; a correction for scale and a correction for ciin'ature of the spectrum lines. If the dis- persion of the star plate differs greatly from that of the dispersion table, the values of r in the table will be too large or small for the star plate. In place of computing the r for each line we apply a correction to v,. obtained as follows: Let a be the difference lietween (he tabular micrometer readings 1 8 Publications of the of the first and last comparison lines used, and b the difference in the actual settings on the plate for these same comparison a-b lines, then the correction for scale == v,. It has the same a ' sign '^s Vj \i a> b and opposite if a <, b. The correction for curvature of the spectral lines may be computed by Ditscheiner's formula,^ which has been found by Adams- to be accurate for long slits. Some observers detennined this correction empirically from lines in the solar spectrum on the assumption that the curve is a parabola. The effect of curva- ture is eliminated in the new Mills sjjectrograph by using a curved slit which gives straight spectral lines. In order to reduce this value of the radial velocity to the Sun, the corrections for the annual and diurnal motions of the Earth are computed from the formulae given by Professor Campbell in Frost-Scheixer, pp. 338-345.^ If r^ be the correction to the observed velocity of the star for the Earth's annual motion, then r- • /v ^ I x n Va= — I a sm (A — O + /) cos p where f ^ =: the Earth's velocity in kilometers per second in its orbit ; A and ft = the longitude and latitude of the star observed ; O =z the Sun's longitude at the time of observation ; 90° — / = the angle which the tangent to the Earth's orbit makes with the radius-vector drawn to the jxjint of tangency. The correction v^ due to the diurnal rotation of the Earth is given by t7 - * ^ ^ ^ v^^=- — K^ sm t cos 8 cos <^ where V^ = the velocity in kilometers per second of a point on the Earth's equator due to the diurnal rotation, and equals 0.47 ; / = the hour angle of the star observed ; S z= the declination of the star observed ; <^ z= the latitude of the observer. 'For this formula and its derivation see Frost-Scheixf.r, p. 15; also, sec an article by Professor Lord, Astrophysical Journal. \"ol. 5, 348. 1897. ' A strophysical Journal, Vol. 11, 309, 1900. .* See Professor Schlesinger's article in Astrophysical Juurttal. Vol. 10, 1-13, 1899; also an approximate method for reductions to the Sun by Dr. Palmer in L. O. Bulletin No. 08, 1906; and a recent graphical method proposed by FIartmann iu Astronomischc Sachrichtcn, Vol. 173. 97, 1906. Astronomical Society of the Pacific. 19 The reduction is simplified by the use of tables giving V^ and i for different values of O, and a table giving V^ for different hour angles and declinations. The value of the lunar correction is small and is usually neglected. It may amount at maximum to about .01 kilometer. Dispersion Formula:. — In order to determine the relation existing between wave-lengths and micrometer readings Camp- BEfx* measured the positions of twenty-two selected lines on a plate of the solar spectnim made with the Mills spectrograph. Taking wave-lengths as abscissae and micrometer readings as ordinates, he assumed the origin of abscissae at A 4330 (i.e. a point near the middle of the plate) and the origin of ordinates at micrometer readings 32.000 corresponding to A 4330. If X is the difference in wave-length in tenth-meters between any line and A 4330, he assumed that the micrometer reading of a line whose wave-length was A (4330 -\- x) was given by R z= 32.000 -j- a + &.r -f fjr^ + ^•*"*- From the twenty-two lines as many equations resulted for the determination of the constants a, b, c, and d, which were solved by the method of least squares. The agreement between the computed and observed micrometer readings was found to be satisfactory not only for the above lines but for intermediate lines as well, throughout the whole region of spectrum employed by him (A 4238 to A 4442). In order to obtain the value of r in the expression rl{ , he obtained by differentiating the above for- dx I mula ,^-=7 — ; ; 5— r Takiue dR equal to unity dx becomes the number of tenth-meters in one revolution of the screw (/. €., r = dx). The wave-lengths used were taken from Rowland's table of solar wave-lengths, and the assumption was made that the wave-lengths of the iron comparison lines used were the same as those of the corresponding iron lines in the solar spectrum. The main objection to the use of the above formula is the great amount of labor involved in making the solution for the constants, in order that the curve should represent accurately the region of spectrum employed. Professor Hartmaxx- proposed a dispersion formula which ' /. c, p. 142. - This is generally known as the Cornu-Hartmann dispersion formula. The form in which it was originally given by Cornu was with the exponent a ^ i- The formula was arrived at, however, independently by IIartmann, by plotting the / 20 Publications of ihe is quite simple and gives a curve wiiicli will rcpreseni witli sufficient accuracy a lon;^ section of the sjiectnim. If j- be the micrometer reading corresponding to the wave-length X, c then .V —.-.-„ ^ — — where .r„, A„, c, and a are constants to be determined by observation. A„ and a characterize the gen- eral form of the dispersion curve and are for the same spectro- graph nearly constant : c is the screw value, and is affected directly by a change in dispersion with temperature ; .Vg is an additive constant which depends upon the position the plate is initially given on the measuring-engine. He determined the constant a in the following manner. Settings were made on five lines in different parts of a sjjectrogram of the Sun. Assuming a =, !, he computed from the two end lines and the middle line the values of the other constants. The residuals from the observed minus the computed micrometer reading.* on the other two lines were of opposite sign. An assumption of o :^ o.Q gave smaller residuals for these two lines. From the residuals obtained, using these two values of a, it was evi- dent that the correct value of a was about 0.6. Using this value of u, he then computed the micrometer settings for the other lines which he wished to use and found that this dis- persion curve represented the observed settings within the errors of observation for the region A 4220 to A 4680. Beyond these points it runs off rapidly. H.vrt.mann computes, from plates made at different temperatures, tables for every 4* difference in temperature of the spectrograph, and uses the table nearest to the dispersion of the star plate for the reduc- tion. With this method of procedure the correction for scale is practically negligible. The value nf r is obtained by ditTer- entiation of the original formula and its value is given by {k — K)'+' , . , where the same constants are taken as m the aC original computation. Most line-of-sight observers have adopted the Coruu-Hart- mann disj^ersion formula for the reduction of their spectro- grams, although the details of the reductions vary. In the computation of the dispersion table for the new Mills spectro- rcfridlve inJex of qiturlE far diFFcrrnt nsve-lcnitlhs. This curvf it an «rui1alrc»ntci] by n\ ciuatioo of ihc ibovr form. Sec Astronomical Society of the Pacific. 21 graph we used the fommla with a =^ i, divided tlie spectrum froni A 4340 to A 4630 into three sections, and conijjntcd a set of constants from three lines for eacli section. Tlie continuity of the curve was assured by taking the last lines of the first and second sections as the first lines respectively of the second and third sections. The representation of the observations was found to be satisfactory. The dispersion table of the Sonthern Mills sjiectrograph was computed, placing a=^ 1, from only three lines for the whole region. The residual differences from the observed values, when plotted against the wave- lengths as abscissae, gave an S-shaped curve from which corrections to the computed values were read off. Professor Kbost' prefers to reduce each of his plates inde- pende«tty of any other plate: i.e. he computes a dispersion table for each plate. Three lines of the comparison spectnnn chosen for their sharpness and for their proper spacing ( one near each end and one near the middle of the spectnnn) give the values of the constants Ao, .v,,, and c in the Cornii-Hart- mann formula where a^i. He then computes the wave- lengths of the comparison and star lines measured. The differences between the computed values of the wave-lengths of the comparison lines and those given for the same lines in RowL-VNii's tables of solar wave-lengths are taken as "correc- tions to comparison lines." These, aside from the accidental errors of setting, he takes as representing the departure of the fonnnla from an exact representation of the wave-lengths. The corrections for the star lines are interpolated from the corrections for the adjacent comparison lines. He prefers to do this rather than to draw a .smooth curve for the corrections to the comparison lines, fearing the arbitrary smoothing out of such a ciir\-e more than the accidental errors of settings and the more serious effects of errors in wave-length of the coni- jKirison lines. Methods of reduction which depend upon dispersion for- muUc re<|uire an accurate knowledge of the wave-lengths of ihc lines used in lx»th the comparison and stellar spectnnn. Accurate vahies of the absolute wave-lengths are not required, but their relative values must be well determined. For exam- ple, a relative error of ± 0,01 tenth-meter in the wave-length h 22 Publications of ike of any line would produce an error in the velocity for that line of nearly a kilometer. The only system of wave-lengths which is at present available for our purpose is that due to Rowland. and this system has been generally adopted by linenDf-sight observers. It has been shown,' however, that errors in relative wave-length exist in Rowland's tables, amounting in some cases to as much as .01 or .02 tenth -meters. Furthemiore the adjustment of the wave-lengths of the solar spectrum to those of the laboratory metallic spectra was not accomplished in a manner free from objections, so that systematic differences between the two residt. Another diffiailty arises, in the case of obtaining wave-lengths for stellar lines, due to the fact that stellar spectrographs have not sufficient resolution to separate lines which were measured as separate lines by means of the more [Kiwerful instrument used by Rowland. It is the prac- tice of many observers, where two lines merge together to fonn one line in the star spectnnn, to take the mean of the wave-lengths of the component lines weighted according to the intensities given by RfiWLAND for those lines in the Sun. Wave-lengths based on estimates of intensities should naturally be regarded with suspicion, and in fact we do not know until the entire plate h^ been reduced whether we have chosen an erroneous wave-length or not. After we have reduced a num- ber of plates of stars of the same type, we can correct the wave-lengths of those lines which consistently give residuals of the same sign. Comparison lines which consistently fall off the curve drawn for the other comparison lines are cor- rected in like manner. It is known, too, that various stellar lines and blends behave differendy for stars of different types.- It is assumed that lines in solar-ty|>c stars have the same wave-lengths as similar lines in the Sun. In the case of other types the solar lines which occur can be used in determining the wave-lengths of the non-solar lines and blends. In this way special tables are constructed for stars of different types. The two methods of measurement and reduction which fol- low eliminate the sources of errors incident to the above methods as far as it is possible to do so. The first is that due b Asftonomical Society of the Pacific. 23 to Mr. R. H. CuHTiss,' and is calU-ri hy liini "Tlie \'elr,city Stamlanl Method." n. The I'elocity Standard Melliod. — The method is in brief as follows: A standard velocity plate (,1. e. a plate of a source whose velocity is acCTirately known), and the stellar plates are produced, as nearly as jxissible, tmder the same conditions of instrument, exposure, comparison spectra, etc. The meas- ures of this standard plate fix the relative positions of the lines of the spectrum of the source and those of the comparison spectrum for a known velocity. These settings we call our zero velocity table. Now, measure the same lines, comparison and stellar, on the plate of the star whose velocity is to be deter- mined. By a plot of the differences between the settings on the comparison lines of tJie standard and stellar plates the star plate is reduced to the dispersion of the standard plate. If the 'corrections from this plot are applied to the star lines, the differences between the measured positions of corresponding Fraunhofcr lines in the standard and star spectra will be proportional to the difference of radial velocity of the sources producing them. It is usual to take a plate of the Sim or sky spcctnmi as the standard velocity plate, or several plates of either, all reduced to the same dispersion, from which to construct a zero-velocity table. It will be seen that the accu- rate wave-lengths of the lines of either comparison or stellar spectnnn are not required in the above process of reductions, and in fact it is necessarj' to know them only roughly ( to about 0.1 tentb-meler ) for the conipiitation of the factor rf j. The assumption of the method is fundamental to all methods,^ namely, that for solar-type stars the wave-lengths of the lines arc the same as those of the corresponding lines in the Sun. For stars of other tj'pes it is necessary to form special tables for each type. The use of blends is based ujion the assumption that the character of a blended line in the spectrmn of a solar type star is the same as in the Sun, and is not dependent upon the estimated intensities of the component lines made by other obser\-ers. This freedom in the use of blends renders the method of great value not only to those using high-dispersion s|ieclrographs but especially to those using low-dispersion instruments. ■ Ciriiiw, AUrofliyiU .: L. 0. Bxllf Publications of the III. The Sf'ectrocomf'aralor.' — The last method to l>e dis- cussed and the one most recent, is that due to Professor Hartmann. It is in principle the same as the preceding method, except that the star plate is referred to the standard plate directly on the engine, in place of using a table of settings obtained from the standard plate. In order to accomplish this, he has designed a special form of measuring-engine known as the spectrocomparalor. The instrmnent is provided with two plate carriages, one of which is movable. On one uf the car- riages the star piate is placed, and on the other, which is provided with a fine micrometer screw, is placed a standard plate of the Snn (obtained with the stellar spectrograph). The microscope has two objectives so arranged that the images of portions of the two plates are brought, by means of total reflecting prisms and a reflecting surface, to foais in the same plane and in the field of one eye-piece. Three strips of the surface of one of the prisms are silvered. These act as dia- phragms in the path of rays coming from the Sun plate and as reflectors in the path of rays coming from the star plate. One of them cuts out the centra! strip of the Sun spectrum and throws into its place the central strip of the star spec- trum. The other two cut out central strips of the compari- son spectra of the Sun plate and throw into their places central strips from the com- parison spectra of the star plate. The arrangement of the spectra in the field of view is as shown in the diagram. By changing the relative magnifying powers of the two objectives he is able to produce the effect of making the dispersion of the two plates the same. The method of measurement is, then, after proper alignment of the plates, to bring corresponding sections of the two plates into the field of the microscoiie, set the corresponding lines of the two comparison spectra in the same straight line, and read the micrometer head. Tlie Sun plate is then moved along Astronomical Society of the Pacific. 25 by the micrometer-screw until corresponding lines in tlie solar spectrum are in the sanie straight line with those of the star spectrum. The difference of the readings in the two positions is the displacement of the star lines relative to the solar lines, and is proportional to the difference in radial velocities of the star and S«n. The s|)ectmm is divided into several sections for each of which these settings are made. The plates are then reversed and the measures repeated, care being taken that the second measure is made at a point of the screw 180° from that of the first. This method of procedure eliminates the physiological error dependent upon the positions of the plates and the periodic errors of the screw. The mean of the dis- placements in the two positions multiplied by the rfj (he calls it s) for each section gives for each the value (' — !'„, where K* is the radial velocity of the star and I',, the radial velocity of the Sun. In taking the mean,' the values l'^ — ('(, for the differ- ent sections are not of equal weight, since the displacements in ihc violet region of the spectrum, where the dispersion is greater, are measured with a higher percentage of accuracy than those in the region of longer wave-lengths. Assume that the prob- ahle error of the measure of the line displacement is the same for all sections. Then the values I'^ — l'„ ^^ sd should receive weights proportional to - in taking the mean. 1 he mean =: M^ ^ - ' _ ^- -^ :^ ^— y He now puts / — zS^and since 5rf= J (Srf, + 2(i,). where rf, and rfj are the displacements in the direct and reverse meas- ure, it follows that M.j= f (2di -|-2rf.). This leads to a very simple method of computation. Take the sum of the dis- placements in the direct and reverse measures and multiply by a factor which is a constant so long as the same regions are used and whose values are computed for all combinations of regions that are used. The product — M^. This corrected for the velocity of the original Sun plate (F,) gives the radial velocity of the star relative to the observer. The reduction to the Sun is made in the usual way. ^Iw a •pcctrum of onlir iwo o 26 Publications of the The great advantage claimed for the method, aside from those which it possesses in common with the velocity standard method, is that we are able to measure and reduce, in an hour or so, a plate of a star of a type rich in lines (several hundred on a plate) and practically utilize all the material on the plate. With the older methods to make such a measure and reduction utilizing all of the lines on the plate would require one or two days. In Conclusion. — For the measure and reduction of spectro- grams of stars of the earlier types, the use of the Cornu- Hartmann dispersion formula will suffice, in as much as the spectra of such stars consist of lines due to the simple gases, the wave-lengths of which have been accurately determined in the laboratory. The measure and reduction of spectrograms of stars of the solar and later types will be accomplished with great saving of time and labor, and, moreover, by a method free from some of the uncertainties of wave-lengths by the use of the spectro- comparator. If the observer is not provided with such an instniment, the standard-velocity method would be used, in preference to any dispersion formula method, at least until a system of wave-lengths of the requisite accuracy is available. For the case of later type stars it will be necessary to make corrections for the variation of lines with spectral type. It should be noted, however, that the corrections for some lines are positive while for others they are negative, so that the effects due to the variation of lines in stellar spectra of different types are to some extent compensating in radial velocity deter- minations. Mt. Hamilton, Cal. Astronomical Society of the Pacific, 27 OPPORTUNITIES FOR SOLAR RESEARCH. By George E. Hale. It is safe to say that every astronomer would prize an opportunity to observe any of the fixed stars from a position where its disk would appear as large as the Sun. It does not seem probable, however, that such observations of stellar phenomena can ever be made, except in the case of the Sun itself. For it should ever be borne in mind, when considering the importance of solar research, that our most intimate knowledge of stellar • phenomena must be derived from solar observations. In the case of the other stars, we mav determine their positions, measure their radial velocities, observe their brightness, and analyze their light, but we have no means of studying the details of their stnicture, which must be under- stood before we can advance far in the solution of the great problem of stellar development. Thus we are driven back to the Sun, and forced to the conclusion that this typical star well deserves our most serious attention, and the application of every available means of research. One cannot but be impressed, when considering the Sun from this standpoint, with the comparative neglect of the numerous opportunities awaiting the student of solar physics. It is possible, by the application of easily available instruments, for any careful student, wherever situated, to solve solar problems of great importance. If space permitted, it could be shown that almost all of the apparatus required in such work can be constructed at very small expense. For our present purpose, however, let us assume that the observer has at his disposal one of the coelostats so commonly employed in eclipse work. If this coelostat has a rather thick mirror, which is frequently resilvered. it may be depended uixmi to serve well for solar work, provided that the mirror is shielded from sunlight during the intervals between the exposure of photographs, and that these exposures are made as short as possible. We may assume that the sunlight is reflected from the coelostat mirror to a second plane mirror ( which should > Reid before the MxronomicB) ami .\5fr0ph.vsical Society o! .\mcrka, 'Scn* \otV, December, tgoS. 28 Publications of the also be as thick as possible) and from this mirror to an objective, which should have an aperture of at least six inches and a focal length of from forty to sixty feet. In place of this objective, a concave mirror, of similar aperture and focal length, may be employed. This apparatus will furnish the necessary means of forming a fixed solar image, of large diameter, within a laboratory, where accessory apparatus can be mounted. Let us now consider briefly some of the investi- gations that can be undertaken. DIRECT PHOTOGRAPHY, The routine photographic work, done under the direction of the Greenwich Observatory, provides ample material for the study of the positions and motions of sun-spots, but special investigations may well be undertaken with the aid of direct photographs. The important thing in all solar work is not merely to make obser\'ations of some single phenomenon, but to carry on two or three series of carefully correlated obser- vations, so designed as to throw light on one another. For example, Mr. Maunder has recently found that the rotation periods of sun-spots in nearly ihe same latitude show differ- ences as great as those encountered in passing from the equator to the highest latitude in which the spots are found. The cause of such differences may well be a subject of most careful investigation. The proper motions* of spots, which are a.ssociated with their period of development, must be fully taken into account. We might also make the hypothesis, merely for the purpose of testing the question, that the rotation period of a sun-spot depends upon its level with respect to the photosphere. For this reason it would be desirable to investigate, in connection with the Study of rotation, the question of the level of sun-spots. A simple means of doing this will be mentioned later. But it may be addecUhere that the question of level raises other considerations, which should not be left out of account. It is probably worth while to investigate photographically the old Wilsonian hypothesis, since visual observations have proved .^n discordant in attempts to determine the relative widths of the preceding and following penumbra of spots at various distances from the center of the Sun. As a sun-spot is depressed below the level of the surrounding facuhe, the vexed question of the visibility of 1^^^^^ Astronomical Society of the Pacific. 29 the umbra near Ihe limb may depend upon whether ihe faciila; are present or missing on the sides lying in the line of sight. It is quite possible (hat the temperature of the umbra may varj' with its distance alxjve the photosphere. Thus correlation beWeen observations hearing on spot level and observations of spot s])ectra is desirable. SPECTROSCOPY. The spectroscopic study of solar phenomena has been greatly retarded through delay in adopting suitable instruments. The short-focus spectroscopes attached to equatorial telescopes are admirably adapted for visual observations, but in photography their linear dispersion is much too small to realize the full resolving power of the grating employed. In laboratory work, on the contrary, while the spectroscopes have been sufficiently powerful, they have usually been of the concave grating type. where astigmatism interferes seriously with the study of solar details, and the solar image on the slit of the spectroscope has been so small that the individual phenomena, in any event. could not be separately distinguished. The preparation of a powerful spectrograph of the Littrow type is an extremely simple matter. A small slit, mounted on a short metallic tube, is supported immediately above a long narrow photographic plate. The wooden support for plate- holder ane borne in mind. It is perhaps commonly supposed that the spectrohelioKraph is necessarily an expensive instniment. out of reach of the average observer. As a matter of fad. however, a sjiectro- heliograph capable of giving the best results can easily be constnirted of niaterinls ordinarily available in any observatory or physical laboratory. It is sufficient, for many piirjMses, to photograph only a narrow zone of the solar image. In this case small lenses will suffice for the collimator and camera, and smalt prisms for the optical train. The lenses and prisms may be mounted in wooden supports, on a wooden platform, rolling on four steel balls in V-shaped tracks. The motion of the instp.mient across lite solar image may easily be produced by a simple screw, driven by a small electric motor. Such a spcctroheliograph was used to good purpose at the Solar Obsen-atory before the permanent instniment was completed. Brief mention may be made of some of the numerous investigations possible with snch an instrument. It hai recently been fotind at the Solar Observatory that the dark hydrogen Aocculi. photographed near the Sim's limb, are slightly dis- placed with reference to the corresponding calcium rtocculi. In general, they lie nearer the limb. This probably indicates that the absorbing hydrogen clonds are on the average at a higher level than the brilliant calcium clouds. This subject deserves careful investigation, extending over a considerable jjortion of time. The type of s])eclroheliograph just referred to is as suitable for the purpo.se as any instrmnent that can be conslnicted. Another question, which seems to be somewhat n»ore difficult to solve, is the actual difference tn elevation of the calcium flocculi. as photographed in the H, and !I.; lines. Indeed, it is still a question as to how important a part tlie dense calcium vapor plays in determining the form of the H, flocculi. These objects resemble the faculae so closely that they appear practically identical with them, though slight differences, which are apparently genuine, are occasionally found. .Another methoil of investigating this whole question of levels is affordeil by the spcctroheliograph. It will be remcm- J bered that when ihe level of sun-spots was last under discus- sion reference was made In the relative radiation of Ihe umbra and neighboring photosphere, corresponding lo diflferent distances from the center of the Sun. Ii was pointed out that when the spot approaches the linib its radiation decreases less rapidly than that of the photosphere. The natural con- clusion was that the spot lies at a higher level than the photosphere, and thereby escapes much of the absorption prorluced by a comparatively thin layer of absorbing matter. Recent observations at Mt, Wilson have shown, however, that the proportion of violet light in sun-spots is much smaller than in the case of the photosphere. As it is known that the violet rays underfjo much more absorption near the Sun"s limb than those of greater wave-length, it is obvious that the light of the spot would suffer less absorption, even if it were at the same level as the photosphere. Thus the only proper method of invest! gatinfj this question will be through the use of monochromatic light. The spectroheliograph affords a simple means of accomplish- ing this. It is only necessary to make photographs of Ihe spot and adjoining photo.sphere, corresponding to various distances from the Sun's center. The camera slit should be set on the continuous spectrum (not on a line), preferably in the violet or ultra-violet, since the change of absorption would be most felt in this region. In order to make photographic comparisons easily possible, the intensity of the photosphere should be reduced to approximately the intensity of the nmbra. by means of a dark glass, mounted over the collimator slit, but not covering that part of the slit through which the light of the umbra passes. It is obvious that a large image of the Sun will be required in this work. The spectroheliograph can be applied to other studies of absorption. The H, flocculi. for example, are reduced in brightness near the Sun's limb much more than the H^ HoccuH. presumably because the latter lie at a higher level. These differences can be studied photometrically on spectroheliograph plates made for the purpose. In the same way Ihe H, tloccidi can be compared with the facula;. Since it is a question just what level is represented by the background (between the flocculi) in calcium, hydrogen, or iron photographs, the instni- ment should be arranged so as to permit photometric com- Astronomical Society of the Pacific. 33 parisons of this background with the photosphere, photographed with light from the continuous spectrum immediately adjoining the calcium, hydrogen, or iron line employed for the flocculi. These new applications of the spectroheliograph have only recently occurred to me, and are mentioned because of their suitability for use with instruments containing prisms of ordi- nary height, capable of photographing only narrow zones of the solar image. Numerous other problems might be men- tioned, such as the comparative study of H,, Hj, and H3 photographs, and of calcium, hydrogen, and iron images ; the distribution of the flocculi in latitude and longitude; their varying area, as bearing on the solar activity and on terrestrial phenomena ; and their motion in longitude, as measuring solar rotation. But limitations of time forbid more than a mere reference to work and methods the details of which are dis- cussed elsewhere. My purpose has been accomplished if I have shown that with comparatively simple instrumental means any careful observer may secure important results. In much of this work it is desirable that investigators occupied with similar problems should co-operate with one another. The Interna- tional Union for Co-operation in Solar Research was organized with this end in view. It has already inaugurated solar studies on a common plan in several different fields, and is preparing to extend the range of its activities in the near future. NOTE ON THE DISTRIBUTION OF DOUBLE STARS IN THE ZONE + 56° TO + 90'.^ By R. G. Aitken. The main object of the survey of the sky that has been in progress at the Lick Observatory for the past seven years is to accumulate data for a statistical study of the number and the distribution in space of the double stars whose com- bined magnitude is brighter than 9.1 of the B. D. scale, and whose angular separation is less than 5". This survey is now well advanced toward completion, so far as the sky area ^ Read before the Astronomical and Astrophysical Society of America, New York, December, 1 906. north of — 22" Declination is concerned, and it becomes a matter of interest to ascertain what kinds of data it is likely to yield. In general, the various 4° zones into which the sky was divided for this survey have not yet been completely examined, the winter hours of Right Ascension, from 7'' to 14''. being considerably less advanced than the remaining portion. But the entire area north of -\- 56° has been examined, and I have tabulated the results. Some of these tabulations and my con- clusions based upon them I desire to present briefly. The region named was divided into eight zones, of which Professor HussEv examined four,. — namely, + 60° to -f 64°, + 64° to -<-68°. +76° to +80°, +80° to +84°, and the writer the remaining four. Professor Hl^ssev included the 9.1 11. D. stars in his search, while I examined only those as bright as y.o. In the following discussion only the stars to 9.0 are inchided. As the area north of + 60° was almost entirely exaniiiicd with the 12-inch telescope, while about one half of the zone, -f- 56° to +60°. was examined with the ^fi-inch, the latter is considered separately. It has been the ex]>cricncc of lioth observers that, under good conditions, a double star with nearly equal components will be recognized with certainty with the 12-inch telescope if the distance is as great as o".25; in fact, we have each discovered several pairs with that instrument whijse distances. measured later with the ,^6-inch, were found to lie well under o".25. If the two components differ two or more magnitudes, we cannot be sure to detect the duplicity if the distance is much under i". If the distance is 2" or more, a companion as faint as 13 or i^'/i magnitude will be seen readily. Since every previously known double star as bright as 9.0 magnitude was carefully identified in the course of the search, the fact that they were first seen with telescopes of very dif- ferent apertures ha.'i no bearing upon the present discussion, so that the results given for the zone -|- fto" to + 90° may be considered to be based entirely upon the separating power of the 12-inch telescope. By actual count of the .'(tars on the charts used in the search. I find that in the region north of + 60° we have examined I2.2<:)<) stars of 9.0 magnitude or brighter. Oi the?c. 294 were Astronomical Society of the Pacific. 35 known double stars, and 259 more were found to be double during our survey, giving a total of 553 pairs in this sky area. This includes seven bright stars with distances exceeding 5", and excludes duplicates. That is, when we have found that one component of a Struve or other known pair is itself double only the closer pair is counted. It appears, then, that one star in 22]/^ in this region is a close double within the separating power of a good 12-inch telescope, a ratio somewhat smaller, as I have reason to believe, than will be found to hold for the sky in general. The tables that accompany this note exhibit the distribution of these pairs. Table I gives the number of new discoveries and the number of previously known double stars in each zone and for each six hours of Right Ascension. Table II combines the new and old pairs for each hour of Right Ascension for the whole region and for the two zones + 60° to + 68° and -\- 68° to 90° separately. Table I. + 60° to + 90° • Quadrant I. o^ to 6^. Doable Stan. Stan to Ratios. Ratios. Zone. New. Old. Total. 9.0 Mag. New D. S. to 9.0 Stan. D. Stan to 9.0 Stan. 84*' to 90^ 0 4 4 107 I : • • ■ • 1 : 26.8 80 to 84 2 5 7 193 I : 96.5 I : 26.2 76 to 80 7 10 17 330 I : 47.2 I : 19.4 72 to 76 14 10 24 418 I : 29.9 I : 17.4 68 to 72 II 12 23 574 I : 52.2 1 : 23.0 64 to 68 21 21 42 691 I : 33.0 I : 16.5 60 to 64 25 31 56 1041 I : 41.6 I : 18.6 Quadrant II. 6h to 12^. 84** to 90^ 3 0 3 no I 36.7 I : 36.7 80 to 84 4 3 7 193 I : 48.2 I : 27.6 76 to 80 2 2 4 281 « • • • I : 70.2 72 to 76 6 7 13 337 I : 56.2 I : 25.9 68 to 72 5 7 12 405 I : 81.0 I : 33.8 64 to 68 10 12 22 519 I : 51.9 I : 23.6 60 to 64 12 14 26 639 I : 53.2 I : 24.6 Quadrant III. I2h TO 18 • 84' to 90^ I 3 4 130 I > • ■ • ■ I : 32.2 80 to 84 2 5 7 191 I : 95.5 I : 27.3 76 to 80 5 3 8 288 I : 57.6 I : 36.0 72 to 76 5 4 9 372 I : 74.4 I : 41. 1 68 to 72 10 7 17 46r I : 46.1 I : 27.1 64 to 68 12 6 18 545 I : 45.4 I : 30.3 60 to 64 12 II 23 610 I : 50.8 I : 26.S 36 Publications of the Quadrant IV. 18I1 TO 24^. Double Stan. Stare to Ratio*. Ratios. Zone. New. Old. Total. «.0 Mac. Sew D.S. to 9.0 Stare. D. Stare to 9.0 Stare 84** to 90'* 2 2 4 "7 I : 58.5 : 29.2 80 to 84 3 7 10 219 I ' : 73.0 21.9 76 to 80 9 6 15 328 I : 36.4 : 21.9 72 to 76 15 12 27 412 I : 27.5 15.3 68 to 72 14 16 30 587 I : 41.9 19.6 64 to 68 21 21 42 965 . I • : 46.0 23.0 60 to 64 26 53 79 1236 I : . 47-5 : 15.6 Summary. Quadrant I 80 93 173 3354 I : 41.9 19.4 II 42 45 87 2484 I : 59.1 28.6 III 47 39 86 2597 I : 55-3 30.2 IV Folal 90 -259 "7 294 207 553 3864 12299 I : 42.9 18.7 r I : 47.5 22.24 Table II. Ratio s OF Double Stars to Stars 9.0 OR Brighter, BY Hours of R . A. R. A. Zone 4- 60** to -f 90**. Zone -f 68** to 4 90*>. Zone -1- 60** to -!- 69"*. oh 28 624— I 22.3 12 : 262=1 : 21.6 16 : 362 = 1 : 22.6 I 33 : 644= I : 19-5 18 : 278=1 : 15.4 15 : 366=1 : 24.4 2 29 : 611 = 1 21. 1 13 : 293 = I : 22.5 16 : 318 = 1 : 19.9 3 27 547 - I . 20.3 8 : 275—1 : 34.4 19 : 272 = I : 14-3 4 31 : 497 = I : 16.0 13 : 277 = I : 21.3 18 : 220 = I : 12.2 5 25 431 = 1 : 17.2 II : 237 - I : 21.5 14 : 194 = 1 : 13.9 6 II 439=1 39.9 6 ' 226 _ I : 37-7 5 : 213 — I : 42.6 7 14 432—1 30.9 6 : 239—1 : 39.8 8 : 193 I : 24.1 8 16 : 411 -I : 25.7 5 : 211 — I : 42.2 II : 200 — I : 18.2 9 19 : 416— I : 21.9 13 : 221 = I : 17.0 6 : 195 = 1 : 32.5 10 10 : 394— I : 39.4 3 : 211 = I : 70.3 7 : 183=1 : 26.1 II 17 : 392-1 : 23.1 6 : 218=1 : 36.3 II : 174=1 : 15.8 12 9 : 375 = I : 41.7 7 : 2io — I : 31-4 2 : 155 = I : 77-8 13 II 414=1 : 37.6 6 : 226 I : 37-7 5 : 188=1 : 37.6 14 10 : 375 = I : 37.5 6 : 190— I : 31.7 4 : 185 = 1 : 46.2 15 21 462= I . 22.0 7 : 260— I : 37.1 14 : 202 = I : 14.4 16 16 : 480=1 30.0 9 : 268 = I : 29.8 7 : 212 — I : 30.3 17 19 491 — I 25.8 10 : 268=1 : 26.8 9 : 223 = I : 24.8 18 25 . 524 = I . 21.0 13 . 272 = I : 20.9 12 : 252 = 1 : 21.0 19 24 650 = I : 27.1 10 . 259 = I : 25.9 ' 14 391 = I : 29.4 20 25 : 557 — 1 22.3 11 : 257- I 23.4 14 . 300=1 : 21.4 21 43 : 696=1 : 16.2 13 : 248-1 : 19.1 30 : 448=1 : 14.9 22 44 : 686-1 : 15.6 18 319=1 : 17.7 26 : 367 = I : 14. 1 23 46: 751 = I : 16.3 21 : 308=1 : 14.7 25 : 443 = 1 : 177 Astronomical Society of the Pacific, 37 Quadrant. SUMMARY. I 173 : 3354= I : 19-4 75 : 1622 = i : 21.6 98 : 1732= i : 177 II S7 : 2484= I : 28.6 39 : 1326= i : 34.0 48 : 1158= i : 24.1 III 86 : 2597 = 1 : 30.2 45 : 1432 = 1 : 31.8 41 : 1165=1 : 28.4 IV 207 : 3864= I : 18.7 86 : 1663= i : 19.3 121 : 2201 = i : 18.2 Total 553 : 12299= I •* -22.24 245 : 6043= i : 24.7 308 : 6256= i : 20.3 It is at once apparent from these tables that the double-star distribution follows in a general way the distribution of all stars to 9.0 magnitude, and if the numbers in Table II are plotted the resemblance of the curves is striking. But an unexpected feature of the distribution is the fact that the double stars are relatively as well as absolutely more numerous in the richer skv areas, the numbers in the four c|uadrants of Right Ascension being very nearly as 2 to i to I to 2 4 while the numbers of the stars to q.o magnitude are about as 1.3 to i to i to 1.5. When the zones + 60° to + 68^ and -{- CiS^ to -j- 90° are taken separately the same relation is found in each. Mv next effort was to determine whether a different relation would be shown by the closer pairs or by the brighter pairs. The pairs under 2" were separately tabulated, then those under i'\ then the very close pairs, J/^" or less, and finally the pairs as bright as 7.5 magnitude. It is not necessary to give the details, but the results by quadrants are as follows : — 1. 11. III. IV. No. Ratio. No. Ratio. No. Ratio. No. Ratio. Under ^/j" 15 1:224 9 1:276 11 1:236 24 1:161 1 76 1 : 44 37 1 : 67 40 i : 65 80 i : 48 2 113 1:30 56 1:44 66 1:39 132 1:29 5 173 1 : 19 87 1 : 29 86 1 : 30 207 i : 19 7.5 Mag.or brighter 49 i : 68 23 1 : 108 18 1 : 144 63 i : 61 It is clear from an inspection of this table that the closer pairs, which may safely be classed as binary systems, follow the same general law of distribution as do all the pairs here considered, and also that magnitude does not materially affect the question. In fact, I find that the average magnitude of the closer pairs in the second and third quadrants is slightly greater, numerically, than that of the corresponding pairs in the other two. So far as this factor goes, therefore, rather more difficult pairs were detected in the second and third quadrants than in the first and fourth. The result is not 2^ Publications of the affected by the time of year in which the work was done, as only nights of good seeing were used, and, besides, the search in each quadrant extended over from six to nine months. It may therefore Ije accepted as a fact that in the sky area from + 60° to the North Pole, double stars of all classes up to 5" separation are relatively more numerous in the region richest in stars to 9.0 magnitude, — that is, in the region of the Milky Way. The zone + 56"" to + 60° contains 4,257 stars as bright as 9.0 that were actually examined with the telescope. The fourth quadrant was almost wholly surveyed with the 12-inch, the first with the 36-inch, and the other two about in equal parts with the two telescopes. Of these stars 114 were known double stars and 130 more were found to be double, making a total of 244 pairs, or a ratio of i to 17.4. When the numbers of double stars and of stars to 9.0 in each hour of Right Ascension are plotted the two curves again show a very marked similaritv. Grouped by quadrants, we find the following relations: — Sun to 9.0. Double stan. Ratio. I 1413 98 I : 144 n 716 35 I : 204 III 672 30 I : 22.4 IV 1456 81 I : 18.0 Thus in this zone, too, we find that the double stars are rela- tively more numerous in the regions richest in stars to 9.0 magnitude, though the curve is somewhat affected, as one would expect, by the fact that the fourth quadrant was exam- ined with a much less powerful instrument than the other three, especially the first. When the ratios are taken bv zones of Declination, we nnd I Zone. Ratio. Zone. Ratio. -f 84** to 4- 90** I : 30.9 + 68M0 + 72° I : 24.7 -f 80 to -h 84 I : 25.7 +64 to +68. I : 21.9 -r 76 to -h 80 I : 27.9 + 60 to -f- 64 I : 19.2 -L- 72 to -h 76 I : 21. 1 +56 to +60 I : 17.4 The charts used in the survey give evidence of local irregu- larities in the distribution of the double stars, the ratio in some areas of 15 to 20 square degrees being as high as i to 7 or 8 and in others as low as i to 50. The study of these irregu- larities is deferred to the time \s'\\en \.Vve >n\\o\^ wotVVv^tix Astronomical Society of the Pacific. 39 hemisphere shall have been examined, when a division of the sky into small sections of approximately equal area will make it possible to decide whether there is any marked tendency toward gregariousness on the part of the double stars and also whether, as a whole, they are distributed symmetrically rela- tively to some plane, — as, for instance, that of the Milky Way. Lick Observatory, December 4, 1906. ASTRONOMICAL OBSERVATIONS IN 1906. ■1 VIade by ToRVAi.n Vai Kohl, at Odder, 1 Denmark. II.\BLE St.\rs. • '.?«*•' Jan. 20 : Z-c. 1 A _ _ l>b. Apr. 8 invisible. Aug. 31 : 14 : e. Aug. • 1 > b'. 13- I step < e. 19 Dec. 4 : 3 steps < e 24 : — b'. 9: id. 27 : id. 23: invisible. S Ursa . Majoris} Jan. I ■ S — g. May 23: e. 19 ; f. July 26: invisible. Feb. 28: I step < e. Aug. 19: -g- Mar. 14: -d. l d. Aug. 27: id. .Apr. 2 : id. 3^: id. ^ < f 4 steps > d. ■ ( 9 steps < c. Sept. 5: I step > f . 5' 8: f d. 10: id. 10: id. 12: id. 12: id. 14: 4 steps < c. 19: id. 22: id. 21 : I step < e. May II : -d. 1 23: id. » N'ide the slcetcb in the Pubiications A. S. P., No. loo, p. 16. 'Vide the sketch in the Pubiications .4. S. P„ No. 73, p. 56. 40 Publications of the Sept. 24 : id. Dec. 4 : I step > d. 27 : e. 9 3 steps > d. Oct. 11: -d. 23 e. Nov. 10 : 4 steps > d. 13 : id. T Ursw . Majoris} Jan. I : T-d. 1 Aug. 31 : id. 19: I step > e. Sept. .S : =:b. Feb. 28 invisible. 8' : id. Mar. 14: id. 10 : id. 19 : id. 12 : id. 29 : id. T ^^ f c. Apr. 5 : id. 19 10 : id. 21 : I step > c. 12 : id. 23 : id. 14 : id. 24 : id. 22 : id. 27 : c. May 5 : id. Oct. II : I step < d. July 26: I b. Nov. 10. 13 : =:f. Aug. 19: -b. Dec. 4: invisible. 24 : id. 9 id. ( b. W Pi ';gasi.'^ Jan. I : W I step > e. Oct. II : I step < g. 2 : id. Nov. 10 : ~R. 19 : I step > c. ^3 : -f. July 26 : invisible. Dec. 4: I step > e. Aug. 19: c. * n is a star bet ween W and b. ss c ygni.^ P M. Jan. 2, 6'' : SS < g. Aug. 24 , lo*' : e. 20, , 6*^ : I step < g. 27. 10*^ : c. Apr. 7, ,14^- c. 14, 9^ : < f . 3i» '^ • Kb. 22, g^ : < d. Sept. 5. lo*' : c. July 26, IT**: e. Sept. 8, 10'' : d. 28, Tnh. ^ <^- II, lo** : I step > e '^ -Of. 12, 9** : id. Aug. 19, IQh . g* I9» 9*^ •• < R- • g is the faint companion -star next c towards Fast. * Vide the sketch in the Publications A. S. P., No. 22, p. 63. ' Vide the sketch in the Publications A. S. P., No. 60. p. 2^. 'Vide the sketch in the Publications A. S. P., No. 100. p. 18. Astronomical Society of the Pacific, 41 Sept. 21, 9-: id. 24, 9^: = h. Oct. II, 9": -g- Nov. 10, O': id. 13. &>: id. Dec. 4, 6^: 6, 6^: 9, ii»»: II, 6**: 23, 6^: I step < c. = d. = e. id. Y Tauri (B. D. + 20^.1083) . As comparison-stars I have used A = B. D. 20°. 1095 (7^.4) and b = B. D. + 20°. 1073 (8™.2). A third star, B = B. D. + 20°. 1 093 {7^.3), I always find smaller than A. Jan. 2 : >b. 19 : id. Mar. 2 : >A. 14: id. 19: • =A. 20; >A. 29: I step > A. Apr. 2 ; id. Apr. 5: id. 12 3 steps > A. Sept. 27 : > A. Nov. 13: = A. Dec. 4 : a little > b. ^^ . |b. 9 *2^ : id. This irregular variable star seems to have had its greatest brightness about the spring and summer of 1906, while in the year 1905 its brightness had not reached that of the star A. TV Cygni. This star oscillates in brightness a little about 9^.5. I have compared it with the stars b and c in the sketch by A. Stanley Williams {A. N. 3629) and always found T V < b. Apr. 7, I4*> : TV = c. July26.iiH:{>- ^^ id. Dec. 4, id. id. Aug. 27, 10^ Sept. 25, 12^ Oct. II, 9*»: Nov. 10, 6** 23, 6*^ { ! >C. c. 20"ia.m. New Moon..'. ** 13, 10 5 p.m. New Moon... ** 12, 11 6 a.m. First Quarter. " 21, 5 10 p.m. i First Quarter. " 20. 12 38 p.m. Full Moon... ** 29, II 44 a.m. : Full Moon " 27, 10 5 p.m. The Sun passes the vernal equinox and spring begins about 10 A.M., Pacific time, March 21st. Mercury is an evening star at the beginning of March, setting about an hour and one half after sunset, and will be 44 Publications of the an easy object for a few rlays about that date on clear evenings. It comes to greatest east elongation on March ist, i8° lo'. This is a much smaller greatest elongation than the average, as it comes less than three days after perihelion. The planet approaches the Sun quite rapidly after the first few days of the month, passing inferior conjunction on the night of March 1 7- 1 8th and becoming a morning star. It then moves rapidly away from the Sun, reaching greatest west elongation on April 14th. Its apparent distance from the Sun will then be 27° 36', which is fifty per cent greater than its distance at the time of greatest east elongation in March; but the conditions for visibility are not nearly as good, as Mercury is now 13° south of the Sun, and rises less than an hour before sunrise, so that it will be impossible to see it with the naked eye. Venus is still a morning star, rising 2^ 20™ before sunrise on March ist, i^* 38*" on April ist, and i^ 20™ on April 30th. The planet passed greatest west elongation on February 8th, and is now nearing the Sun, but the main cause of the dimi- nution of the interval between the rising of the planet and of the Sun is the southward motion of the planet relative to the Sun. Venus passes about 1° 39' north of the vernal equinox on the afternoon of April 26th. At 7 a.m. April 21st, Pacific time, it is in very close conjunction with Saturn, passing 0° 38' north of the latter. Mars rises at i** 36™ a.m. on March 1st, at 12^ 50™ a.m. on April ist, and at ii** 52™ p.m. on April 30th. During the two-months period it moves 31° eastward and 2° southward, from Scorpio through the southern extremity of Ophiuchus into Sagittarius, and during the latter part of April is in the neighborhood of the **milk-dip|)er" group in the latter con- stellation, a little farther north. Its distance from the Earth diminishes from 121 millions of miles on March 1st to 70 millions on April 30th, and its brightness at the latter date is consequently about three times as great as it was at the former, rather more than a magnitude, as the brightness of stars is usually reckoned. From now on it will be a conspic- uous object until some months after opposition. Jupiter is in fine position for evening observation. On March ist it sets a little before 3 a.m. and on April 30th at a little before 1 1 : 30 p.m. It is in the constellation Gemini, Astronomical Society of the Pacific. 45 and moves about 7° nearly due eastward during the two months. It is in a region richer in bright stars than any other in the sky. Castor and Pollux are east of the planet. Aldeb- n is west, and the bright stars of the Orion group, with Cants major and Cants minor, are to the south. Saltirti is an evening star on March ist, but sets about lialf an hour after sunset, and is therefore too near the Sun for naked-eye observations. On the night of March 8-fjth it passes conjunction with the Sun and becomes a morning star. The planet does not reach a great enough distance froui tlie Sun to be seen in the morning twilight until well into April. At tbe end of the month it rises about an hour and three quarters before sunrise. It is in the constellation Pisces, and moves about 6^ east and 3° north during the two months. The phenomena displayed by Saturti's rings during 1907 will He of great interest to astronomers. The rings are so nearly edgewise to the Earth throughout the year that very little can be seen of them with a small telescope, but large telescopes may be able to show some new and interesting tilings. Since the autumn of 1891 both Sun and Earth have been above the plane of the rings, but on April 12th the Earth passes through this plane and from that time until July 25th the Earth and Sun are on opposite sides of the plane and the face turned toward us is the unilluminated face. i)n July 25th the plane of the rings passes through the Sun, and until IJctober 4th both Sun and Earth are on the same side of tlie plane. On October 4th the Earth again passes through the plane, and for the remainder of the year the Earth and Sun arc again on opposite sides. Early in 1908 the Earth again passes through the plane, and for the succeeding fifteen years the Earth and Sun are both below the plane. Questions as to the transparency and thickness of the rings may possibly be solved. The year 1907 affords the best opportunity for the study of these phenomena which we have had for many years. Saliim is in opposition in September, and the planet is fairly well placed for observation from the middle of April to the end of the year. In 1891 Sun and Earth were on opposi.te sides of the ring for only one month, and this period began only ten days after conjunction, so that the planet was too near the Sun for satisfactory observation. Uranus rises shortly before 4 .\.m. on March ist and shortly fubltcattons of befurc niidniglit on April 30th. It is still in SagHtaniis of the "milk-dipper." Neptune is in Gemini, a few degrees east of Jupiter. THE CAUSE or EARTHQUAKES AND MOUNTAIN FORMATION.' jH Bv T, J, J, See. ^^1 Soon after the great earthquake of April i8th, the writer en- tered npon a general examination of the cause of earthquakes, because the explanations put forth to account for that phenom- enon seemed inadequate. The conclusions finallv reached have been embodied in a memoir just published in the Procefdings of the American Philosophical Society at Philadelphia: they had also been given in a public address at Leland Stanford Jr. University, on November igth. The principal results are the following:— ( I ) Volcanic activity, earth tiiiakes, mountain formation, the feeble attraction of mountains noted in geodesy, the formation of plateaus and islands, and the great sea-waves which fre- quently accompany violent earthquakes, are all due to one com- mon cause. — namely, the developnent of steam within or just beneath the Earth's cmst. chiefly by the .secular leakage of the ocean -Iwtloms, which are subjected to fluid pressure of nearly one thousand atmospheres by the superincumbent depth of water. (2) As the development of steam is general under the seas, the strain under the Earth's crust would find relief chiefly around the margins of the oceans. The Pacific Ocean not only has high mountains all around it. but the laud is rising geologically, and seven eighths of the active volcanoes of the world surround this great ocean. No active volcano is over al>oiil one himdred miles from the ocean or other large body of water, while many are submarine, and volcanic islands are forming all the time. Of the vapors emitted by volcanoes 999 in 1000 parts is steam, which again confinus the dependence Astronomical Society of the Pacific. 47 on the sea inferred from the remarkable geographical dislribii- tion of these vents. (3) Heretofore the mountains have been explained by the contraction and secular coohng of the Earth; but the explana- tion is verj' inddeijiiate. Rev. O. Fisher has shown that the actual mountains are about one hundreii times higher than this llicory will account for, and this discrepancy can only indicate the unsoundness of the theory. In his paper on the rigidity of the heavenly bodies (.-1. .V. 4104J the writer has shown that no ctirrents circulate within the Earth, either now or at any time since the formation of the crust ; the cooling has there- fore been confined lo the crust, and the secular shrinkage has been wholly insensible throughout all geological time. The mountains therefore iiave been formed by the sea, and not by the secular cooling of the Earth. This explains why the moiin- lain chains are generally parallel to the seashore. (4) Mountains, plateaus, and islands have all been upheaved by the injection of steam-saturated lava, which dries and be- comes pumice, some of which is blown out of those mountains which become volcanoes. The mountains arc underlaid with pumice, and hence their feeble attraction noticed in geodesy. Earthquakes are more general than volcanoes, which break out where the elevation of the land opens an outlet through the crust; as a rule, the volcanoes are near the centers of the earthquake belts, and always near the sea. In most world- shaking earthquakes lava is pushed under the land, from beneath the sea; hence the terrible shaking which is so de- structive to life and property, in South America the land along the seacoast is frequently upraised ; and a seismic sea- wave follows. (5) The seismic sea-wave is due to the sinking of the sea- botlom, after its support has been weakened by the expulsion of lava under the adjacent coast. Hence after the earthquake the water drains away to fill up the depression, the currents meet in the center and raise a ridge, and when this collapses the great wave returns to the shore lo add to the horrors of the earthquake. The Amies are pushed up along the coast, while the adjacent sea-bottom is sunk down into a trough. If the earthquake uplifts the coast, and thus forms mountains along the seashore, while the wave is due to the collapse of the sea-bottom, it is clear that the coast is being packed underneath 48 Publications of the Astronomical Society, &c. with lava, while the bed of the sea is being undermined by the expiilsi<;n of material to raise the mountains. ( ()j During the great earthquake in Alaska, September 3-20, i8(X). which has been most carefully investigated by Professor K. S. Tarr and Lawrkxck Martin,* the uplift of the land at the maximum amounted to 47^/3 feet, while elevations of seven to twenty feet were common, though slight depressions also occurred in a few places. Professor H. D. Curtis, of the D. (). Mills exjiedition of the Lick Observatory, refx^rts from Santiago- that the harbor at X'alparaiso was found to be ten feet shallower after the earthquake of August i6th. These observations give the key to the problem of earthquakes and mountain formation. The indications of nature are plain enough, if we will only follow her teachings and examine the evidence on its merits. The first duty of the investigator is to study for himself: imi)ortant truth is not discovered with- out impartial judgment, labor, and thought. The reader is referred to the pai)er in the Proceedings of the American Philosophical Society for further details of the complicated processes arising in earthquakes, mountain forma- tion, and kindred phenomena. N.WAI. OllSEKVATOKY. MaRK ISLAND. CaL.. February i, 1907. • Bulletin of till' Ci-olotiical Society of .'hiic^ii-i. May, ioi>6. - Cf. .irfiitniiut iif Xovcmhcr 2. ig'»6. -VOTES FROM PACIFIC COAST OBSF.RVATORIES. TIm Note on Mt. Hamilton Weather. Lick Observatory is now passing through the most severe snow blockade that it has experienced at least since 1889-90. Between January I2t!i and 16th the snowfall ex- ceeded fifty inches. The latter part of the fall was attended by considerable wind, and long stretches of the road were drifted full. The snowfall was remarkable for the low altitnde to which it descended. At Smith Creek it amoimted to eighteen inches, and tlie fall extended down to within one hundred or two hundred feet of the level of the Santa Clara Valley. No stage has reached the summit since January 12th, and at the flate of writing, January 22d, we are not expecting the stage to come to the summit for another week at least. The wires which gave us telephone connection with the outside world were broken down under the great weight of snow and ice which collected on them. On two days we did not attempt to communicate with the stage, which ascended as far as Smith Creek, On other days the mails and supplies were carried up over the snow by members of the staff. Fortunately, no illness developed, and the inconvenience of the blockade has thus far not been serious. The winter has been unusually cold, stormy, and cloudy. The precipitation to date corresponds to about twenty-one inches of rainfall. \\r^ \\\ Campreli.. Os THE Relation between Stellar Spectral Tvpes and THE Intensities of Certain Lines in the Spectra.' During the past summer, in connection with the measurement of spectrograms obtained at the Mills Observatory in Chile by Professor Wrkikt. an investigation of the individual spec- trom lines was begim. with a view of determining whether 'A noTc cmnplelf aecounl of Ihii invoiigaiion ii puLilishrd in Licit Obienaiifry 50 Publications of the there is a shift of any of the lines which is progressive from spectral type to type. Several lines were found which undergo such a progressive change, as is indicated by the radial veloci- ties obtained from them. An examination of Row^land's tables shows that in most but not all cases studied lines apparently single are in reality blends of two or more close components. The nature of the variations found is such as to indicate vary- ing intensities of the same components rather than the presence or absence of different components in the different types. It was the intention,' when sufficient data had been obtained, to make comparisons with the enhanced and weakened lines in the spark and arc spectra. When a list of sun-spot lines^ in the region covered by the Southern Mills plates became avail- able, a comparison with these was made instead. The investi- gation was limited to stars of types F to Mb inclusive on the Harvard classification. In this classification the Sun is of type G. The principal result of the comparison is the very strong indication that the physical conditions in the stars as we pass from the F to the Mb type vary in the same direction as from the Sun to the sun-spots. It is not intended to convey the impression, however, that any one type has been found in which the conditions are exactly the same as in the sun-spots, though an early K type is probably nearest to it. In the Mb type the relative intensities of the lines as shown, both by their appear- ance and their residuals, have gone far beyond what they are in the Sun, whereas in the F type they much precede the con- dition in the solar spectrum. Adams has shown a striking similarity to exist in the intensities of sun-spot lines and of the corresponding lines in the spectrum of Arcturiis (type K), while Hale and Adams- have made a similar comparison of intensities for a Ononis (type Ma) in the region A 5393 to A 5703- A large number of lines might be mentioned which change greatly in intensity and appearance as we proceed from the F to the Mb type, this change being frequently very prominent even from the G to the K type, and which are not included in Adams's list of lines affected in sun-spots. Among the most ' '*Sun-spot Lines in the Spectrum of Arcturus," by Walter S. Adams, Astro- physical Journal. Vol. ^4, p. 69, 1906. ^ AstropUysical Journal, Vol, 23, p. 400, 1906. Astronomical Society of the Pacific. 51 striking of these are the Cr lines, A 4254.5 and A 4274.9, which become very strong, wide, and diffuse as we follow the scale of stellar types. A few cases of contradictory evidence have also been found, in which the residuals show a decided shift in the opposite direction from that which would be expected from the intensities assigned to the components in sun-spots. Among these the line A 4435.2 may be especially mentioned. For this blend both my value of the wave-length, as deter- mined from the spectrograms, and the progressive trend of the residuals indicate a shift of its center toward the violet instead of toward the red. Some of the observed differences between sun-spots and stellar K type, in which the physical conditions may be similar, may be due to the fact that in the stars this condition is the average condition in their entire atmospheres, while in the case of the sun-spots some effects may be altered by overlying layers of gases and vapors or by other local circumstances. Nevertheless the similarities are sufficiently striking to promise much for this line of study. The results here given depend not only upon the appearances of the lines, but primarily upon quantitative measurements of their positions. It was thought possible that for variable stars of large light changes traces of velocity variations of some of the lines might be found, corresponding to small changes in spectral type as the stars varied from maxima to minima and zfice versa. In the case of o Ceti actual changes in the character of the spectrum are well-established facts, though up to the present no appreciable changes in the wave-lengths of any of its spec- trum lines have been observed — leaving out of account the large displacements of the bright hydrogen lines. A com- parison of the available measures of rj Aquilce, a variable star of the fourth class with a range of only 0.8 of a magnitude in light variation, showed evidences of variations in the positions of some of its lines from light maximum to minimum similar to the variations that were found from type to type. A further study of this variable star is desirable to establish definitely the exact character and amount of these variations. The following few examples are typical of the progressive variations that were found for the different types. The intensi- ties in the Sun are Rowland's, and those in sun-spots and in Arcturits are taken from Adams's article (/. c). 52 Publications of the X 4352.908 Fe — Intensity in Sun, 4 1 In sun-spots, 6-7; in A returns, 7-8; 53.044 V — Intensity in Sun, o ^ widened toward red. Residuals (in km.) : — F FSGandFSGPec. G G5K 1 IC K2MandK5M Mb — 3.0 — 3-7 + 0.8 — 0.7 + 1.6 + 2.1 + 3.6 + 3.4 + 1.5 + 1.0 — 0.6 + 3.1 + 3.4 + 3.0 + 4-9 — 1.0 + 1.7 + 2.2 + 0.8 + 2.6 + 3.0 + 4-6 + 1.5 — I.I + 2.8 + 1.4 + 1.4 + 1.0 + 4.7 —3.5 ±00 + 2.6 + 4.8 + 3.9 + 3.9 + 1.7 + 3.1 + 1.5 + 2.2 + 0.8 + 2.0 + 0.9 + 2.2 + 0.8 — 0.2 + 4.3 + 1.9 + 3.2 + 2.2 + 4.4 + 3.3 + 3.0 + 6.5 pan<» • " + 0.8 V + 3.6 + 3.0 — 1.0 V -\-2.2 + 4.7 X 4468.663 Ti — Intensity in Sun, 5; in sun-spots, 4-5; in Arcturus, not affected. Residuals : — F F8G G G5K K K5M Mb — 1.3 —2.2 —0.3 +1.4 +2.8 +2.7 +5.7 +6.8 — 4.1 —0.3 —1.5 +0.9 +2.6 +^.7 +0.8 +7.0 + 1.7 —2.9 —0.9 —0.7 +3.9 +4.3 +6.3 +3.5 — 3.0 —0.9 —0,9 + I.I +1.5 +2.5 +6.1 — 3-7 +1.4 +2.7 +1.0 —0.3 +4.7 +4.8 — 2.1 +0.6 +1.9 +4.7 +1.9 -\-2.2 +0.6 +4.7 +1.7 + 0.4 +0.4 +5-2 +5.9 — 0.4 —1.5 + 1.2 —3.0 + 1.3 +3-3 + 0.7 — O.I Means : ^^ v ^ — 2.1 —1.0 —0.9 +0.2 +1.3 +4.3 +4.7 X 4314.964 Ti — Intensity in Sun, 1 1 15.138 Ti— Intensity in Sun, 3 VNot included in list of sun-spot line*?. 15.262 Fe — Intensity in Sun, 4 J Residuals:— p ^ k ksm Mb Means: +1.1 — 1.4 — 2.0 — 2.7 — 5.0 X 4435.129 Ca — Intensity in Sun. 5; in sun-spots, 6*1 .32 Fe — Intensity in Sun, 2; in sun-spots, VlnArcturus,^. Residuals :- "«' afi^citd. J P FSGandG GSKandK K5M Mb Means : — 4.0 — 1.7 + 0.3 + 2.5 ± + 1.8 ± Astronomical Society of the Pacific. 53 The establishing of these variations in the wave-lengths of some of the lines with spectral type will make necessary the exercise of great care in the selection of lines in radial velocity determinations, and a proper allowance for the type. Mt. Hamilton, December 14, 1906. Sebastian Albrecht. Honors Conferred upon Professors Aitken and Hussev. The Paris Academy of Sciences has conferred the Lalande Prize for 1906 upon Professor R. G. Aitken, of the Lick Observatory, and Professor W. J. Hussev, formerly of the Lick Observatory, and now Director of the Detroit Observa- tory' at Ann Arbor. The prize usually consists of a gold medal and a small sum of monev. It has on several occasions been divided between two astronomers, as in the present case. The following paragraphs are translated from the report of the award published in Comptcs Rendus for December 17, 1906: — •' No branch of sidereal astronomy presents to-day a higher in- terest than that relating to the study of double or multiple stars. " Among contemporary astronomers who have undertaken this studv with success, Messrs. R. G. Aitken and William J. Hussev,^ astronomers in the Lick Observatory, are in the first rank, because they have each discovered more than 1,200 new doubles ;- and in almost three fourths of these pairs the dis- tance of the components is less than two seconds of arc. . " These astronomers have, moreover, measured with care all these pairs in such a manner as to fix the present relative positions of the components. '* In addition, they have made observations upon the fainter satellites of Jupiter, Saturn, etc. '* These are results of the highest importance, and the Com- mission proposes to divide the Lalande Prize between Messrs. R. G. Aitken and W. J. Hussev. " The conclusions of this report are adopted by the Acad- " ^* W. W. Campbell. Mt. Hamilton, January 22, 1907. * Professor Hussey has recently left the Lick Observatory, in order to become Director of the Detroit Observatory of the University of Michigan. — Comptes Rendus. *Thc number i,aoo refers necessarily to those published. Professor Aitken, up to 1907, has discovered more than 1.500 double stars, and Professor IIussev had discovered more than 1,300 up to the time of his departure in June, 1905.— w. w. c. 54 Publications of the The Oriut of Ho 212 = 13 Cutj} In number 104 of these Publications a note on this interest- ing binary system will l)e found giving my measures in 1905, which indicated a revolution period of about yYi years. Measures made in TO06 confirm this conclusion, the companion- star being now within a few degrees of the position it occupied in 1899. Using Dr. Ske's measure in i8c)9 and my own made in the following years (the only ones known to me), I have derived the set of elements here given. They satisfy the observations on which they were based within the probable error of meas- ure, and also satisfy the two early measures by Hough in 1886 and 1887. It is now certain that 13 Ccti has a shorter period than any other known visual binary except 5 Equulei, A well-defined proper motion adds to the interest of the system. ELEMENTS. P = 7.42 years. w = 5i°.75 T "= 1905.28 n = 50 .40 e = 0.74 i = ± 48^.05 a = o".2i4 Angles increasing. January 24, 1907. R. G. AlTKEX. XoTE ox Comet li 1906 (Metcalf). This comet was discovered near opposition by Rev. J. H. Metcalf, of Taunton, Mass., from a photograph taken November 14, 1906. The discovery position is 0 = 4** 4"™ 35*, S = — 2° i5'.8. No preliminary elements were computed here for either this comet or Comet Thiele, which was discovered at about the same time, as the observatory force was crippled by the illness of Mr. Ein arson. Assistant in Astronomy, so that no time was available for comjniting. l^ater, however, two sets of elements based upon longer arcs were derived, and the results have been jni Wished in Lick Observatory BnUcfin No. 108. The first set is based upon Path's observations of November 17th, 25th, and December 5th. It was found that no parabola could 1)e passed through *A more detailed account is given in Lick Ohscn'atory BuUctin, No. \\o. Astronomical Society of the Pacific. 55 these positions. They are represented, however, by an elliptic orbit in which the comet has a period of 6.9 years. An observation by Dr. Aitken, made December i8th, is not very closely represented by these elements. It was therefore decided to correct them by means of this observation. The resulting second set is also elliptic, giving a period of 8.2 years. The plane of the orbit is inclined nearly 15° to the plane of the ecliptic. The comet made its nearest approach to the Sun, 150 millions miles, October 5th. It is a new member of Jupiter s family of comets. At the time of discovery it was very faint and was receding from both the Earth and the Sun. At present it can be seen in only the largest telescopes, its brilliancy being less than one fourth of what it was at discovery. Russell Tracy Crawford. Berkeley Astronomical Department, January i8, 1907. GENERAL NOTES. Stellar Photometry. — Publication \o. 33 of the Carnegie Institution of Washington, "Researches in Stellar Pho- tometry," by John A. Parkhurst, Instnictor in Practical Astronomy in the University of Chicago, was issued during Xovember of the year just closed. The quarto volume of 192 pages contains obsen^ations and disatssions of twelve variable stars of long period observed by Mr. Parkhuhst between 1893 and 1905. During the first seven years the observations were made mostly at Marengo, Illinois, with a 6-inch New- tonian reflector by Bkasheak. Since 1900 Mr. Parkhurst has been connected with the Yerkes Observatory, and the 12- and 40-inch refractors of that institution were used in addition to the 6-inch reflector. During the first period the observations were made visually by the method of Argeuwdeb, but during the second period 3 wedge photometer, devised by Professor E. C, Pjckkkixg, was used for the most part. In the introduction the anthor states that his work is addressed to the solution of tour problems in photometry, and the statement of these is admirably prefaced as follows: — " The problems of stellar pholomelry arc closely connected wilh many cosmic qiieslions, primarily with Ihe light changes of variable stars ; but they have an equally important bearing on the questions of stellar illstribinion and evolution. It has been said by good authorities that it is of more importance to measure the light than the place of a star, and if one considers merely the astonishing nmnbcr of variable stars now being discovered, it will be admitted that the importance of stellar photometry can scarcely he overestitnaled. The material lierc sub- mitted is the natural outgrowth of the writer's variable-star work, the plans being extended as the instrumental and other facilities were improved. '■ The following contribution is offered toward the solution of several photometric problems, among them being : — " (1) The accurate determination of complete light-curves of twelve variable stars of long period, having faint minima. " (a) The question of behavior of variable stars daring their faint stages which can only be observed with the largest apertures. " (3) The adaptation of the Pickering 'equalizing wedgo photometer' to tlie determinations of magnitudes, " <4) The photometric measurement of very taint magnitudes, and iheir relation to estimate'* founded on the limit of visibility of different apertures of telescopes." Astronomical Society of the Pacific. Under the headings "Essentials for good visual compari- M>ns" and "Essentials for good photometer measures," Mr. Pakkhl'RST gives also in the introduction some very whole- some advice which it would be well for all variable-star observ- ers to read. Chapter I is devoted to a description of the instruments used, and especially to the consideration of the constants of the equalizing wedge photometer. The following twelve chapters are devoted one each to the Iwelve variable stars observed, — T Andromeda, \' Andromeda, \>i' Andromeda, R Comer, RU //itch/w, RV Here id is, S Lyra. S Cv£Hi. SX.C.v.?'ii'. \' Dclphini, Z Cassiopeia!, Y Cassiopeia. These are for tlie most part new variables discovered duri the last decade of the nineteenth cenliiry. Each chapter con- tains a short historical statement; a photograph of the field of the variable made with a 24-inch reflector; various tables giv- ing the individual observations, the comparison -stars, constants for reduction, observed maxima and minima, etc. ; the magni- tude-curve ; the light-curve ; the mean light-curve ; and conclu- sions giving period of star and peculiarities of its light-cur\'c. The obser\'ations and reductions have been made with minute care and great thoroughness, and it is evident from the tests applied that the results obtained by Mr. Parkuurst are pos- sessed of a high degree of precision. The magnitudes of the stars observed lie between 7.5 and 17, the greatest range of any one variable, V Delphini. being nine magnitudes, from 8 to 17, a really remarkable range. The only other variable having an observed range of more than 7.5 magnitudes being xCygm, 4.5 to 13.5. The average range for the twelve stars is 5.8 magnitudes. The periods of these lie between 259 and 529 days, the average being 3112 days. .\ large number of long-period variables have periods approxi- mately a year in length, and the average period is over three hundred days and apparently approaching closer to a year. It seems hardly likely, however, that these facts have any ■vpccial significance. It is well known that in stars of this class the increase in light is accomplished in less time than the decrease, the ratio between the two parts of the period being about five to six. This feature is well shown in the light-curves of jdl the twelve stars observed by Parkuurst, except S Cygui. \ox \\V\\cV Publications of the M — Til is almost exactly one half tlie period. The iiiequahly between increase and decrease of light is greatest for \ Dclphiiii, the ratio being abont five to eight. Its period is 529 days, one of the longest known. This star shows, then, three distinctive characteristics among the twelve stars, its period is the longest, its range is the greatest, and the inequal- ity between the two parts of the period is the largest. The elements obtained by the author for the twelve stars are derived from observations of ninety-five maxima and ninety- three minima. The observations, however, were not confined to the epochs of maxima and minima, bnt were carried on, as far as possible, over the whole period, and the special feature of the volume is the well-determined mean light-curves which have been derived in each case. It is now generally recognized among variable-star investigators that it is just as essential to determine ihe form of the light-curve as to determine the length of the period. Several good series of variable-star observations from which light-curves may be deduced have been published without graphic representation of the curves, and the usefulness of the investigations considerably decreased thereby. In the concluding chapter there is given, among other things, a comparison between the theoretical and the observed limits of vision of the three telescopes employed in the investigations. The theoretical limits were computed by the use of Pogson's well-known formula and the agreements are remarkably close. The seventeenth magnitude is the limit of the giant 40-inch refractor. It is to be hoped that Mr. Pahkhurst may be able to con- tinue in this line of work, for investigations such as these, planned with care, executed with skill, discussed with precision. are most urgently needed in variable-star astronomv- S. D. T. Double-Star Orbits. — By his long-continued devotion to the study of double stars and by the quality of the many orbits he has published, Dr. W. Dobkrck lias well earned his posi- tion as one of the leading authorities in this branch of astron- omy. That his interest does not diminish with the years is evident from the number of his investigations that have recently appeared. The latest (Astraiioinische Sachrichttn. 4i44-4i^§) are new orbits of three oS tV\e best V.wQViT\ ol "itK. Astronomical Society of the Pacific, 59 binary systems, — namely, I^Cancri, o) Leon is, and 53062 = Hi 39. There are other recent orbits of all three of these systems that represent the observed motion up to the present time with a high degree of accuracy, and it is perhaps questionable whether so much labor as is represented by these new discussions was wisely bestowed. Nevertheless it is always interesting and instructive to compare the results obtained by different com- puters, using different methods of solution, especially when, as in the case of the three stars named, the orbits are based substantially on the same material. The periods of the three systems, according to Doberck, are 116, 105, and 60 years respectively, and the motion is not specially rapid at the pres- ent time in any one of them. The new elements of mLeonis and 2 3062 do not differ materially from the other recent orbits, and only serve as additional evidence that our knowl- edge of the motions in these systems is now fairly accurate. In the case of f Cancri, Dr. Doberck's results differ more from Seeliger's than might be expected, in view of the fact that the latter represent recent observations within the prob- able error of measure. The two sets of elements are as follows : — p. T. (» a o) Q i Seeligeb: 59y.11 1868.11 0.381 o".858 25o*'.26 80°. 19 ii*'.i4 Doberck: 60 .08 1870.65 0.339 o .856 183 .65 * o .00 Angles decreasing. If one might venture any criticism upon such painstaking work as Dr. Doberck's, it would be on the ground that he does not make much use of the measures of distance, basing his results almost exclusively upon the angle measures. The question might also be raised whether elaborate least-squares solutions are justified by the quality of the material available, but this question will be answered in due time by the way in which the results thus derived represent the future motions in these svstems. A. On Star Streaming, — At a meeting of the British Associa- tion for the Advancement of Science held at Cape Town, South Africa, August 17, 1905, Professor J. C. Kapteyx read a paper with the above title. It cointained an announcement of * The pUnes of the true and of the apparent orbit coincide in this so\u\\ot\. 6o Publications of the the results of a study of the proper motions of over 2,400 stars observed by IJr.-ujley. The study was taken up for the information it was expected to yield regarding the motion of the Sun among the stars, but certait] anomalies appeared which seemed to indicate the existence of an important and hitherto unsuspected systematic motion among the stars under investigation. It appeared that the proper motions showed a trend toward two points in the sky about 140° apart, lying south of a Orionis and jiSagUlarii respectively. The explanation offered is that a large number of stars distributed throughout all of the regions of the sky covered by the Bradley catalogue partake of a common, or group, mo- tion peculiar to themselves. All of the stars under investiga- tion seemed to belong to one or the other of two groups. This introduces a complication into the problem of determin- ing the apex and velocity of the Sun's way, and Professor Kaptevn desires confirmation from spectroscopic observations before proceeding to the completion of his study. A subsequent study by Mr. A. S. Eddington of the proper motions of the stars contained in the Groombridge catalogue has quantitatively confirmed Professor Kapteyn's conclusion. The 4.500 stars of the Groombridge catalogue include a much larger proportion of faint stars than the Bradley list, and they lie within a smaller area of the sky, all being within 52° of the North Pole. Mr. EmiiNGTON concludes that the two- drift hypothesis is a good first approximation to the actual state of affairs, bnt he is by no means convinced that there may not be other drifts involving a sufficiently large number of stars, and so distributed that account will have to be taken of them in the solution of the problem of determining the Sun's motion among the stars. An abstract of Mr. Eddinc- ton's paper may be found in Observatory No. ^yy. N. Algol Variable RR Draconis. — In Bulletin No. <) of the Laws Observatory of the University of Missouri Professor Seares presents the results of photometric observations of an interesting new variable nf the --ilfiol type, RR Draconis. The period is found to be 2.831079 days. At normal brightness the variable'is of the tenth magnitude, and the decrease in bright- ness at the time of minimum is over three maEn.\tt.\des. The Astronomical Society of the Pacific, 6i exact amount of decrease could not be determined with the telescope employed, for the star was invisible for a period of about two hours in the neighborhood of the minimum. The time occupied in the light changes is about ten hours. The rate of change of light at the steepest part of the curve is over a magnitude in half an hour. This star at minimum is fainter than any other Algol vari- able listed in the Harvard Provisional Catalogue of Variable Stars. Its range of brightness is also greater than that of any other variable of this type, the average range being 1.4 mag- nitudes. S. D. T. National Academy of Sciences. — The autumn meeting of the National Academy of Sciences was held November 20th, 21st, and 22d in the buildings of the Harvard Medical School, Bos- ton. Among the large number of papers presented five were upon astronomical subjects, as follows: "The Work of the Bruce Telescope," by S. I. Bailey, of Harvard University : "Present State of Knowledge as to Motions of the Terrestrial Pole/' by S. C. Chandler, Editor of the Astronomical Journal: **Extent and Structure of the Stellar System," by G. C. Com- STOCK, of the University of Wisconsin; "Sun-Spot Spectra, and Their Bearing on Stellar Evolution," by G. E. Hale, of the Solar Observatory of the Carnegie Institution; "Planetary Inversion and the Tenth Satellite of Saturn/' by W. H. Pickering, of Harvard University. At the conversazione held in connection with the meeting, photographs, slides, and drawings were presented by the Harvard College Observatory and by the Solar Observatory of the Carnegie Institution. The following notes have been taken from recent numbers of Science: — Professor Charles Lane Poor, of Columbia University, gave a public lecture under the auspices of the New York Academy of Sciences and the American Museum of Natural Histor>', on November 19th, on "The Proposed New Astron- omical Observatory and Nautical Museum for New York City." Dr. William H. Brooks, Director of Smith Obscrv^lox^ and Professor of Astronomy at Hobert College, Geneva, 'N . X ., 62 Publications of the Astronomical Society^ &c. has received a medal from the Astronomical Society of Mexico for his discoveries of twenty-five comets. Professor Rajna, of Bologna, is making an appeal for funds to rebuild the observatory there on a new site, and to provide it with instruments suited to modern requirements. Professor Ernest W. Brown, who goes at the end of the present academic year from Haverford College to Yale Uni- versity, has been awarded the gold medal for 1907 by the Royal Astronomical Society for his work on the movements of the Moon. Mr. Sydney S. Hough, chief assistant in the Royal Ob- servatory, Cape of Good Hope, has been appointed His Majes- ty's Astronomer at that observatory on the retirement of Sir David Gill. Dr. Sidney Dean Townley, astronomer in charge of the International Latitude Observatory at Ukiah, California, and lecturer in astronomy in the University of California, has been appointed to an assistant professorship in the department of applied mathematics at Leland Stanford Junior University. Dr. Townley will assume the duties of his new position with the beginning of the next academic year in August. NEW PUBLICATIONS. Andoyer, a. Coiirs dastronomie. Premiere partie: Astro- nomic theorique. Paris : Hermami. 1906. GiUBS, J. W. The scientific papers of. New York: Longmans, Green & Co. 1906. 2 vols., royal 8vo. Hill, G. W. The collected mathematical works of. 3 vols. Washington: Carnegie Institution. 1906. $2.50 per vol. Lowell, P. Mars and its canals. New York: ^Macmillan Co. 1906. 8vo. 15 + 393 pp. Cloth, $2.50. Morse, E. L. Mars and its mystery. Boston: Little, Brown & Co., 1906. 8vo. viii + 192 pp. Cloth, $2.00. MouLTON, F. R. An introduction to astronomy. New York: Macmillan Co. 1906. Svo. 18 + 557 PP- Cloth, $1.25. MouLTOX, F. R. A class of periodic solutions of the problem of three bodies with applications to the lunar theory. Re- print from Trans. Am. Math. Society. 1906. 40 pp. Newcomb, S. a compendium of spherical astronomy. New York: Macmillan Co. 1906. 8vo. 18 + 444 pp. Cloth, $3.00. Optical convention, 1905: Catalogue of optical and general scientific instruments. Edinburgh : \\ & E. Murray. 1906. Parkiiurst, J. A. Researches in stellar photometry. Wash- ington: Carriegie Institution (Publ. No. 33). 1906. 4to. 192 pp. Paper, $2.00. Science Year Book, The. Diary, directory, biography, and scientific summary for 1907. London: 27 Chauncy Lane. 1906. 5s. Seares, F. H. The Algol variable RR Draconis. Columbia: University of Missouri. (Laws Observatory Bulletin No. 9.) 4to. 15 pp. Verschaffel, M. l'Abbe. Observations faites au cercle meri- dienen 1904. Abbadia : Observations. Tome IV. 4to. 190-. Athens: Annales de I'observatoire national. Tome IV. 1906. Transactions of the international union for co-operation in solar research. Vol. I. London : Sherratt & Hughes. 1906. Svo. xii -f- 257 pp. Cloth. 64 Publications of the MiNUTKS OF Till-: Mef-tixg of the Doard of Directors held AT THE StL'DEXTS' ObSERVATORV, BeRKELEV, t)N JaNIARV 26, 1907, AT 7:30 P.M. President LnistHNER presided. A (|uorum was present. The min- utes of the last meeting were approved. The following new members were duly elected : — List of Members Elected January 26, 1907. Mr. Charles 11. Crossland 8 Forsythe St., Chelsea, Mass. Mr. Curtis H. Tho.m as Traer, Iowa. It was upon motion. Resolved. That the Committee on Publication \yc authorized to reprint number 2 of the Publications in an edition of 250 copies. Adjourned. Minutes of the Meetinc; of the Astroxo.mical Society OF THE PaCH'IC HELD AT THE StU1)E.\T.s' (^II.SERVATORV at Berkeley ox January 26, 1907, at 8 p. m. President Leuschner called the meeting to order, and introduced the lecturer of the evening. Professor W. W. Campbell, Director of the Lick 01)ser\atory, who read his paper on '*Thc St)lar Corona," illustrating his remarks by a number of lantern-slides. A committee to nominate a list of eleven Directors and Committee on Pubhcation, of three members, to be voted for at the .A.niuial Meeting to l)c held on March 30, 1007. was appointed as follows : Messrs. J. K. Moffitt (Chairman), S. D. Townu:v, C. 1). Perrlve. J. I). Galloway, O. von Geldkrn'. A committee to audit the accounts of the Treasurer and to report at the Annual Meeting in March, was appointed as follows : Messrs. Chas. S. Cl'shinc. (Chairman), Daniel Slter. B. A. Bairik Adjourned. Aiironomical Society of lite Pacific. 65 OFFICERS OF THE SOCIBTY. H*«. S. CutuiHti Firit rict-Preiidinl . U. D,>*cacK Stcend Vict-Pttsidtnt Mr. W. W. C*ii«eu. Third Vict-Preiidrnt . K. C. .MT«I., <;.„.,„,.. «r. K. R. Ziu. / ^tCTiiBrwt Mi. P. K. Ziu. -Ircaiurer Beard af Dirtci.iri—Mcta*. Aitkeh, ItMCocx, Di'dckkaltex, CAurnELL, CuoCKtii. HISC, ILUE, LevKHHEI, RlCHIlDtOH. S»ECKEL9. ZlEL. Ffmtt C»mniilirf—Mgim. Cvsumc. C>ocK», RtCHMPSOX. £-<.iHMiKf< a* PubliitalieH—ilHtn. Aitiikn, Tt.*»l*». Newki.i;. Libra'f Commiltte—ilr. voir Geldesk. Mr. Hicha«osok. Mri. Sckilh. C0»im» OH Ibt CBmrl-iltdnt — MttsJi. Camfkll (ex-ofticia). I1i. NOTICB. Tlic alttnlian of mw menbert it called lo .Vrlicle VIII o( Ibe By-Lawt, which , avidei Ihit the annual lubaeriplion, paid oxi ciKtion, cavers Ihc calendar year only. Subcei)aen I annual paymcnu are due on January I9I of each aucceedini pouible. Duo soil br mail ihould be direcled to Ailranomical bocielr of the , PaeiBc, Se6 FnnUin Sirect, Sin FranclKO. It It inleiuled thai each member ol Ihe Sociely iball receive a -copy of each one aO mbaequeut rears. If there have been tunCortunately) any omia^oni in Ihls K 7. 1. nested that the Secretariea be at once notified, in order Ihat the ben may be lupplied. Memberi are requested lo preEcrve the copiei ■atieni of ihe Sociely al Kill to Ihem. CAice each year a Iitle-pase and :be piecedini uumben wi!1 sIhi be &en< tp Ihe memben, who can then bind the irombetj togeUier inla ■ volume. Complete •□lumes Car piii years will ■ba be MiMlied. lo nwmben only, u far as Ihe itock in hand is auflicient, on the ler viibin the United Suies can oblaln books (rom the Society's library by PnnUiii Street San Franciscu, who will remrn Ihe book and the card. The Committee on Publication dciir^ to say (hat the order in which papers are prinril in tht rublicoHonx is decided siDtply by convenience. In a ^neral Pa^ i1!Mn^C^ bi'pnnled in ™gi*en"nural^r"( Se Sw^ii(iDi.°'sfould*b^"rn I Ibc hands of the Commillee not Uwr than the aoth of the month preceding date ^^M 1 pobliealion. It it not pouible lo send proof iheets of papers to be printed to ^^^B iftrt excused in Ihe papers printed, and for the form of tlieir eapressioH. rests ^^^| Tlie tUlM of p»tMT« for reidina should be communicated to either of the Sec- ^^B .etiries ■* early a* pouible. as well as any changes in addresses. The Secreurjr I in Swi Francisco will send to any member of Ihe Society tuiUble suiionery. ■ — ■ ,(,1 of jbe Sociely. al cosl price, as follows: a Mock of letter paper, 4B ecDli: of nole paper, >; ccnii: a package of envelopes, ij cents. These prices include postage, and should be remitted by money-order or in V. S. postage -nsBU. The seodings are al the risk of Ihe member. Die siiB™r™hould*commIK!Ste'' Jilh" "The "fS^r'eUry An""nDmiM"' SMiciy' "ol Ibe Pacific." 806 Franklin Streel. San Francisco, in order Ihal arrangcmema may ■ - nsportation, lodging, etc, PVaUCAlIOSS ISSUED ai-MOXTIILV. Fft" J PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XIX. San Francisco, California, April 10, 1907. No. 113. PRELIMINARY STATISTICS ON THE ECCENTRICI- TIES OF COMET ORBITS.^ By a. O. LEu.*i(HNKR. \'arious investigations of the eccentricities of the orbits of comets have led to the conckision that the majority of such orbits are parabolic. In fact, about three fourths of all comet orbits have been found consistent with an eccentricity equal to unity. This is the main reason why it is generally accepted that a comet orbit is parabolic, unless it can be shown to be otherwise. An accurate knowledge of the eccentricities of comet orbits is of importance in determining the origin of comets. It is, therefore, advisable to study the eccentricities from as many j)oints of view as possible. Two methods of classifying the eccentricities have occurred to me which do not seem to have entered into the analysis hitherto. Both are related to the acairacy of the observational material from which the orbits are derived. One is to classify the eccentricities on the basis of the general accuracy of the observations, the other on the basis of the observed heliocentric arc. Marked progress has been made during the last century in the methods of observation and in the construction of tele- scopes, so that observations have become more and more reli- able, and the number of days during which comets of the same brijjhtness mav be followed has constantlv increased. Ever since the first computation of a comet orbit was made, it has been customary to derive a parabola as a first approxi- mation to the orbit, and to attempt a more general solution only if the deviations of the observed positions from the places com- ' Abstract of address of the retirinsr President of the Society, presented a.t V\v« annual meeting, March 30, 1907. 68 Publications of the puted from the most probable parabola were in excess of the probable errors of observation. This custom has become so thoroughly fixed in astronomy that even now it would be considered absolutely unwarranted to suspect a comet of mov- ing in an ellipse if by a little stretching of the probable limits of observational error a parabola could be found to represent the observed positions. A prejudice has always existed, and exists now, in favor of the parabola. This prejudice is not entirely due to statistical investigations of the orbits of past comets. A further excuse for the same may be found in the fact that the first geometrical and analytical methods for solving a comet orbit were para- bolic. The solution of an elliptic orbit was originally possible only in cases like Halley's comet, where more than one appearance had been observed, so that one of the unknowns, the period, became known. Gauss's general solution had its first application on the as- teroid Ceres, at the dawn of the nineteenth century, and it was not until some time later that general methods were also applied to comets. It is a well-recognized fact that when the observed arc is short and the probable error of observation on a comet is large, the solution of the orbit will be uncertain, or, in other words, in such cases a large number of different orbits will be found to satisfy the observations. The "Short Method" which has been used extensively in the Berkeley Astronomical Depart- ment during the last three years is well suited for estimating the limiting values of the elements. The range of possible periods and eccentricities is far greater than has perhaps been supposed hitherto. A cursory examination of many definitive orbits based on normal places formed from long series of observations shows that in many cases a long- period ellipse* will often answer as well as a parabola. The ellipse is then gen- erally dismissed with the statement that there is no reason to suspect a deviation from the parabola. It would be just as consistent to conclude that there is no reason to suspect that the comet moves exactly in a parabola. In accordance with existing belief regarding the eccentricities of comet orbits. Dr. Kreutz in his biennial reports to the Astronomische Gesell- schaft adopts the parabola whenever it is found sufficient. Before proceeding to an examination of the published lists Astronomical Society of the Pacific. 69 of elements it is therefore well to emphasize that possibly in no case where an ellipse or hyperbola alone is given can the observations be represented by a parabola, but when a para- bola is given the observations may frequently be consistent with an ellipse and sometimes with a hyperbola. If, in spite of this fact, it can be demonstrated that by far the majority of well-determined orbits is elliptic, then the time has come when astronomers should abandon their preju- dice for the parabola, by investigating and stating the com- plete range of possible solutions in each case. Olber's, Galle's, and Winlock's lists were not available when a preliminary examination of the eccentricities was un- dertaken. The excellent list, however, contained in E. Weiss's edition of "Littrow, Wunder des Himmels," is well suited for the purpose of the preliminary investigation, especially because it gives the duration of visibility in days. This list runs to 1885. The results of the preliminary examination were, how- ever, roughly revised just before publication on the basis of Galle's and Winlock's lists and Kreutz's biennial reports to the Astronomische Gesellschaft to IQ04, which latter are con- tained in the Vierteljahrsschrift. Comets discovered between 1885 and 1895 were added to Weiss's list only when the dura- tion of visibility was included in the data at hand. Periodic comets are, of course, counted only for their first apparition. For the purpose of classifying the orbits on the basis of the general accuracy of the observational material, or more nearly of the observed positions, the percentage of parabolic orbits was ascertained for each of three groups, in the order of time as given in Table I. Dates. Table I. -1/55 99 per cent 1756-1845 74 per cent 1846-1895 54 per cent It is safe to assume that there has been a progressive and pronounced advance in the accuracy of observation in these three periods of time. Hyperbolic orbits were not included in the totals on which the percentages of Tables I and II are based. From the more accurate observations of the fifty years from 1846 to 1895 we may therefore conclude that it is no more probable that a comet is parabolic than that \\, \s tvot. 70 Publications of the In Tabic II the eccentricities have been grouped on the basis of the duration of visibility in days. The percentage of para- bolas is given for each group. The comets discovered before 1756 have been excluded in the totals from which these percent- ages were derived, as their orbits can throw little light on the question under consideration. n •• t X- u IV Table II. Duration of \ isibility. e -- i I- 99 days 68 per cent 100-239 days 55 per cent 240-51 1 days 13 per cent These figures are certainly striking. They show that the longer a comet is under observation the more probable it be- comes that its orbit cannot be satisfied by a parabola. This result is in entire accordance with the opinion held by some astronomers that few, if any, orbits are strictly para- bolic. In the last group only eight comets were available, which are all given as elliptic by Weiss, and for one of these Kreutz's later reports give a parabola, which has been adopted, the same as every orbit has been considered parabolic in these tables for which the observations could be satisfied by a para- bola. It is therefore extremely doubtful whether a parabola is definitely established for any comet having remained visible 240 days or more. It would have been better if Table II could have been based on the length of the observed heliocentric arcs, but these are not immediately available, and in a first approxi- mation for a large number of comets the average of the number of days of visibility may be taken to correspond to the average heliocentric arc. Percentages have also been derived for various ranges of eccentricity. These, however, will not be published until the final investigation has been concluded. The average eccentricity of periodic orbits is very high. In applying the short method it has been found that when- ever a short arc yielded a considerable range of periodic solu- tions, a longer arc would yield solutions for the eccentricity nearer the upper than the lower previous limits. The explana- tion of the high eccentricities lies in the nature of things. Long-period comets cannot come within the range of visibility irom the Earth imless their orbits are highly eccentric. The Astronomical Society of the Pacific. ji others must remain invisible, until the power of our telescopes is still further increased. From the average brightness of comets at unit geocentric distance the maximum perihelion distance at which a comet may be seen in opposition from the Earth with the more power- ful instruments may be derived. The values of the eccentricity corresponding to this maximum for a given value of the semi-major axis or period will then be the minimum eccen- tricity which the orbit of a comet of average brightness and of given period must have in order to be visible from the Earth, under the most favorable circumstances. This question will be studied in connection with a proposed further study of comet orbits. The theory that, in general, comets are permanent members of our solar system seems to have been greatly strengthened by the foregoing preliminary statistics. It will be remembered that until Keeler began photographing nebulae with the Crossley reflector the spiral was considered the exceptional form of a nebula. The p)ercentage of double stars is increasing so rapidly that their discover}' either directly, or spectroscopically, or photometrically, or otherwise, is no longer a cause for surprise. It seems emi- nently probable that with further investigation of cometary orbits the parabola will be found to be the exception. Rs^KELEY Astronomical Department, March 30, 1907. THE SOLAR CORONA.^ By W. W. Campbell. Of all the wonders of this and other worlds that it has been my good fortune to see, a total solar eclipse is by far the most impressive, and the Sun*s corona is its central and most beau- tiful feature. The corona appears to have attracted the attention of intelligent observers who dwelt within the shadow- paths, in all ages of our civilization. Plutarch has left an excellent description of its appearance, and occasional later » Lecture delivered before the Astronomical Society of the Pacific on 3?ltvmwy »%» 1P07. Tie lantern slide illustrations are necessarily omitted. 72 Publications of the writers have referred to it. Speculation as to what the corona really is was naturally very meager prior to the middle of the last century, for the custom of dispatching expeditions to study eclipse phenomena had not been inaugurated, and it therefore seldom fell to the lot of any one man to observe two eclipses, either with or without scientific instruments and methods. In Kepler's day, and until less than a century ago, the corona was believed by most men of science to be due to the illumina- tion of the Moon's atmosphere. When it was finally estab- lished that the Moon has extremely little or no atmosphere, the corona was generally explained as a phenomenon of the Earth's atmosphere; and it was not until the year 1870 that the tide of scientific opinion turned toward the Sun itself as the origin and center of the corona. Even as late as 1883, one of the ablest of astronomical physicists published an ad- mirable discussion of the corona as a purely subjective, non- material phenomenon, due to the diffraction of the Sun's photospheric rays at the Moon's edge. The objective existence and solar character of the corona are to-day thoroughly estab- lished, and the erroneous views of our predecessors come as a surprise no doubt to many persons of the younger generation. It is far other\vise with those who are familiar with eclipse history. Take away the spectroscopic method of study, which came nominally in 1859, but virtually, for eclipse purposes, later in the sixties, and take away the photographic plate which was made to bear upon the problem, faintly in the early seven- ties and strongly in the eighties, — ^take these aw^ay, and I think we should still be struggling with the question. Where is the corona situated? Let two of us make a pencil drawing of the same corona, — one of us in Spain and the other in Egypt. The two drawings will be more remarkable for their differences than for their agreements; and what is more nat- ural than to attribute these differences to varying conditions in the terrestrial atmosphere above the two observers, or to the changed influence of the irregularities on the Moon's edge as viewed from the two points of observation. Let the eclipse observer of to-day try to find out something new about the corona, even with the spectroscope, polariscope, thermoscope, and photographic plate, and his respect for the pioneers will be established upon a firm basis. The corona remains a strictly eclipse phenomenon. The I Astronomical Society of the Pacific. 73 commendable efforts of several leading astronomers to observe the corona in full sunlight have unfortunately failed, on account of its relative faintness and its low effective tem- perature, and all the methods now available seem hopelessly unpromising. Given suitable appliances, such as the 40-foot eclipse camera designed by Professor Schaeberle, the corona may be seen faintly and imperfectly during one to three min- utes before totality is complete, and during an equaj interval after totality ends; but we have not been able to make any scientific use of these pre- and post-totality views. Every item in our knowledge of the corona has been obtained during the total phase. Assuming that observable total eclipses occur, on the average, once in two years, and that their average dura- tion is three minutes, no astronomer, in fifty years of activity in following the Sun and Moon, can hope to utilize more than seventy-five minutes in eclipse observation. Making the reasonable deduction of one third for clouds and other deter- ring factors, his maximum expectation during a long life must not exceed fifty minutes. The total duration of observable eclipses for any one observer since the spectroscope and photographic plate have been available scarcely equals a half- hour. Herein lies the chief difficulty of coronal investigation. However, the progress made since the spectroscope showed a bright coronal line, in 1869, ^"^ photographic plates at two stations showed identical coronal stnictures, in 1871, has been so great as to be unique in science. Another difficulty in coronal study is for the most part only vaguely appreciated. The coronal streamers are on the whole radial, with reference to the Sun, and appear to overlie every part of the Sun*s spherical surface. Now, every coronal structure lying within the cylinder occulted by the Moon is entirely hidden from view, and all structure lying outside of this cylinder is seen in projection upon one plane. The pro- jected image of the corona recorded on the photographic plate is complex to an apparently hopeless degree. Every small area in the apparent inner corona is a composite of all the structures lying betwen the observer and the area in question. The tops of streamers pointing nearly toward and nearly away from the observer, the intermediate parts of numerous other streamers, and the bases of streamers nearly at right-angles to the observer's line of sight are all projected upon a eomrcvoxv area. And similarly for all parts of tlie coronal image. There is no known way of resolving the composite image into its elements. Xotwithstanding these and other difficulties, we know much concerning the properties and characteristics of the corona. However, this knowledge has not reached the deductive stage. Our facts are isolated ones. We are not only not able to pre- dict the detailed form of a future corona, but we cannot say why an observed corona has a certain general form. We know so little concerning the origin of the corona and its dejwndence upon the rest of the Sun, that starting dc novo with our present-day knowledge of the main body of the Sun, and no knowledge whatever of the corona, we should be more sur- prised by the existence of a corona than by its total absence ! Taking up first the study of coronal images, it has been established that there is a dependence of coronal forms upon the sun-spot period. At and near sun-spot maximum the general outline of the corona is circular. The polar streamers are as extensive and as brilliant as the equatorial streamers. That this is true of the outer regions of the corona as well as of the inner is shown by both long and short photographic exposures. At or near sim-s]iot minimimi the general form is verv different. The polar streamers are short, faint, delicate, and few. The equatorial streamers, and especially those in the stui-six3t zones or at slightly higher latitudes, are longer than at maximum, and in general there are two broad streamers extending easterly and two westerly from the Sun, several solar diameters in length. These are necessarily but the projec- tions of two sets of long streamers entirely encircling the Sun. Their bases seem to be situated a little further from the equator than are tlie sun-spot zones. These variations in coronal forms with spot activity are now so well established that coronal streamers and spots may safely be said to have a closely related origin. The hooded forms of the inner corona, each covering a conspicuous prominence, can leave no doubt that they and the prominences concerned have had a closely related origin. The great conical disturbance in the corona of igoi, noted by Dr. Pehrine, whose vertex was shown by him to be situated immediately over or very near to the great and only spot on the Sun at the time, can leave little doubt that the disturbed Astronomical Society of the Pacific. 75 coronal structure and the photospheric disturbance indicated by the spot had a common origin. All the evidence is to the effect that the corona is closely related to the rest of the Sun. We do not know the nature of this relation ; but we can safely say that a thorough under- standing of the Sun requires an understanding of the corona. The light radiated by the corona appears to be of three kinds : — 1st. A thin and very irregular stratum, perhaps never ex- ceeding 200,000 miles, and more probably never exceeding 100.000 miles, in depth, lying at the base of the corona and apparently resting upon the chromosphere, gives a bright-line spectrum. The natural interpretation of this spectrum is that the stratum giving rise to it consists of a gas or vapor heated to incandescence; but it has been suggested here and there that the bright lines may indicate an electric glow in the inner corona, such as one gets from a Pliicker tube agitated by an electric current. For my part, there seems to be no real necessity for going beyond simple incandescence produced by the Sun's heat. The element yielding the ten or twelve bright lines* has not been identified with any terrestrial substance. There may indeed be more than one vapor or gas present. It is difficult to conceive how irregular masses of vapor can maintain themselves at great heights above the solar surface, in opposition to the Sun's gravitational attraction. Perhaps the vapor is constantly given off by the solid or liquid particles which seem to form the major part of the inner corona, for these particles must be at a high temperature, under the influence of the Sun's heat. 2d. Nearly all of the light from the inner corona — perhaps ninety-five per cent of it^ — appears to give a strictly continuous spectrum, which indicates a solid or liquid source raised to incandescence. The most reasonable conclusion is that the inner corona consists largely of minute particles maintained at a very high temperature by the adjacent body of the Sun. 3d. The light of the middle and outer corona yields a spectrum which seems to be substantially identical with the solar spectrum — a spectrum containing the usual Fraunhofer dark lines. On this point there is not unanimity of observers. Plcvinel in 1893 ^"^ ^^^ Crocker Expedition of 1901 to » VvaoM gives a It'st of twenty- four corona lines. — Phil. Trans., Vol. 206, p.^S^, \^o6. 76 Publications of the Sumatra and of 1905 to Spain have recorded dark lines, whereas others appear to have observed continuous spectrum, pure and simple. The discordance is difficult to explain. If the dark lines exist, we have every reason to believe that the corresponding parts of the corona consist of minute particles of matter, not shining appreciably by their own light, but principally by virtue of original sunlight which radiates to the particles and is reflected and diffracted to us. The latter view is supported overwhelmingly by a long series of polarization observations. Granted that the corona is com- posed of minute particles which diff^use the sunlight falling upon them, the coronal light should be polarized, radially, very much as sunlight diffused by our own atmosphere is polarized strongly, in planes passing through the Sun. It is true that polarization may be produced otherwise than by reflection or diffusion, — for example, by a magnetic field, as in the Zeeman effect ; but polarization seems to exist in all parts of the corona. The opinions of astronomers as to the materials composing the corona, and as to why the Sun has any corona at all, have been very divergent. Some have belieyed that the corona is composed of meteors, many of them revolving around the Sun, and others falling into the Sun. However, this theory is largely in disfavor, and we need not consider it, though no doubt there are a great many meteors both revolving around and falling into the Sun. Schaeberle's mechanical theory proposes that "the theo- retical corona is caused by light emitted and reflected from streams of matter ejected from the Sun by forces which in general act along lines normal to the surface of the Sun, these forces being most active near the center of each sun-spot zone." To account for the longer streamers in the corona, considering their materials to be ejected by forces analogous to volcanic forces and to be drawn back by the Sun's gravitational power, would require that their speeds on leaving the Sun should be between 200 and 400 miles per second. According to this theory, also, there would be multitudes of both ascending and descending particles. According to Bigelow's magnetic theory, the corona is a sort of solar aurora whose streamers occupy positions corre- sponding to the lines of force in the Sun's magnetic field, just as the Earth's magnetic field seems to cotvtrol the streamers of terrestrial auroras. Astronomical Society of the Pacific. yy When Lebedew, and Nichols and Hull, some five or six. years ago, proved experimentally that light and heat radiations exert a pressure upon all bodies in their paths, it occurred to Arrhenius, and possibly to others, that here is the basis for a satisfactory theory of the corona. If strong radiations press upon exceedingly minute particles, the particles will move away from the source of radiation; the larger and denser particles, speaking popularly,, will travel slowly, and the lighter and smaller particles rapidly. There can be little doubt that matter exists at the Sun's surface in a state capable of being acted upon eflFectively by this radiation pressure. According to this theory, the smaller and lighter particles (more exactly, those having the smallest product of mass and density) would be driven off into distant space, with little chance of returning to the Sun ; and the reimiting of two or more particles would in many cases give gravity the advantage, so as to bring them back to the Sun. It is true that this theory, in common with all the others, leaves much to be explained. For example, it is difficult to say why sun-spot inactivity should produce extraor- dinarily long streamers in the high sun-spot latitudes, and sun-spot activity streamers of equal lengths all over the Sun. I think there is an excellent chance that all these theories have much truth in them. There can be no question that eruptive forces, or convection and evection currents of great speed, exist at the Sun's surface, — responsible for many of the prominences, certainly, — and perhaps they give an outward impulse to the coronal material. The forms of many coronal streamers certainly resemble closely the lines of force in a magnetic field, and we cannot doubt that radiation pressure must be active and effective. But it is scarcely conceivable that the eniptive forces on the Sun can give speeds of 300 or 400 miles per second to the ejected coronal materials, and the radiation-pressure theory renders the supposition of such great speeds unnecessary. At the eclipse of 1900, Abbot made one of the most impor- tant of recent eclipse observations, in that he measured the heat radiation of the inner corona. He found that the corona is effectively cooler than the instrument with which he ob- served. The observation was a delicate one and liable to considerable error. Although confirmation is very V!LT^txv\N?j desired. Abbot's observation is probably approx\tr\a\.eVj cot- Publications of the rect. AisBfiT coiiclucied that the corona ap[)ears "neither 1li reflect much Hght from the Sun nor chiefly by virtue of a high temperature to give Hght of its own, but seems rather to be ^ving light in a manner not associated with a high tem- perature. . . ." This conclusion seemed at first to deny the theory of the corona's constitution outlined above, as ba^ed upon the evidence of the spectroscope and polariscope; but a very illuminating pajter by Ahrhenius has, I think, shown that Ahuot's results on the heal of the corona are in harmony with the view that the inner corona consists mainly of incandescent particles. Arrhenius has determined from computation that corona! particles in the region observed by Aubot must have a tem- perature of about 4.300° C. (8,000° F.). assuming the effective temperature of the Sun's photosphere to be 6,000° C. ; and, therefore, these particles must lie radiating light by virtue of their own incandescence. These particles are so few and so far apart that the effective temperature observed by the bolometer is not at all the temperature of the particles them- selves, but is, so to speak, the average temperature for the incandescent particles and the cold background of space upon which these particles are seen here and there in projection. The total area of the background covered by the iKirticles in projection is an exceedingly minute fraction of the whole area. The spectroscopic and thermometric observations are har- monized within the limits of error of observation by assuming that, in the part of the corona observed, there is but one minute dust-particle for each fifteen cubic yards of space. We should not overlook the fact that the series of incandes- cent [minis in the distant corona affect the eye or the photo- graphic plate just as if ihey formed a contimions and highly illuminated surface, whereas the thermometer in effect averages the radiations from the coronal particles to the instrument and the radiations from the instrument to the cold background of space. The action of our atmosphere in stopping a certain proportion of the beat radiations is also effective and has to be taken into account. The existence of matter in the corona at great distances from the Sim implies that it has come from somewhere- doubtless from the Sun itself. This necessarily implies that motion lias occurred. Is the material of the corona moving Astronomical Society of the Pacific, 79 out from the Sun or toward the Sun, or both, or neither? We have no accurate observational knowledge on this subject. The unusually favorable eclipse of August 30, 1905, offered a hope that large-scale photographs of the corona secured in Labrador, Spain, and Egypt, or in two of these countries, would enable us to detect changes in the coronal structure occurring between the instants of totality in those countries. Dr. Perrine and I have made careful comparisons of the coro- nal images recorded by the Crocker Eclipse Expeditions in Spain and Egypt. A number of fairly well-defined nuclei of the corona existed both east and west of the Sun. As a result of these comparisons we are able to say that there is no certain evidence of motion having occurred in the interval of 70 min- utes which elapsed between the instants of totality in Spain and Egypt. Details of structure within the nuclei have suffered change, but the mass as a whole cannot have moved so much as one mile per second during the interval. Greater speeds might well have occurred in the principal coronal streamers without our having detected them; for their structure is uni- form and regular, and well-defined nuclei are absent. Thus, in the cases where high speeds should perhaps be most nat- urally expected, photographic plates have little power to record them. Measures of motions of approach and recession within the corona by means of the sp)ectrograph are unpromising, for several reasons. The coronal light is intrinsically weak, and exposures are from necessity short. The brighter parts of the corona radiate light forming a continuous spectrum, neglecting- the almost insignificant component which gives rise to bright lines. Even if spectrograms of the middle and outer coro- nal regions could be secured with the Fraunhofer lines recorded in good strength, their inter])retation would be diffi- cult and somewhat unpromising. The slit of the spectrograph would receive light from streamers which radiate in a variety of directions from the Sun. There would be streamers point- ing both toward and away from the observer and streamers occupying positions of all values intermediate between these limits. If the coronal particles were moving outward exclu- sively, the general effect would be to cause a shift correspond- ing to recession, but the lines would be broadened. Pavt\c\^«» moving toward the Sun would in effect displace \n lV\e d\T^c\!\OTv 8o Publications of the of approach, at the same time broadening the lines. It will be easv for the reader to determine the effect of a motion of either kind in a streamer making a given angle with the observer's line of sight, and space will not be taken here to summarize further the general effect. It is evident that a dark-line spec- trum, if one of sufficient density and dispersion could be obtained, would be of great complexity. However, a knowl- edge of the motions within the corona would doubtless be our most effective power in determining the origin of the corona, and the subject should not be abandoned as hopeless. PLANETARY PHENOMENA FOR MAY AND JUNE, 1907. By Malcolm McNeill. PHASES OF THE MOON, PACIFIC TIME. Last Quarter.. May 4, i^ 53m p.m. New Moon " 12,12 59 a.m. First Quarter. . " 20, 5 27 a.m. Full Moon ." 27, 6 18 a.m. Last Quarter.. June 2, 91*20™ p.m. New Moon " 10, 3 50 p.m. First Quarter. . " 18, 6 55 p.m. Full Moon " 25, I 27 p.m. The summer solstice, the time when the Sun stops moving north and begins to move south, occurs June 22d, 6 a.m., Pacific time. Mercury is a morning star on May ist, rising less than an hour before sunrise, and is therefore too near the Sun for naked-eye observation. It moves rapidly toward the Sun, and passes superior conjunction, becoming an evening star, on the night of May 23d-24th. It then moves rapidly away from the Sun and a little northward. Shortly after June ist it remains above the horizon an hour after sunset, and this period in- creases to about an hour and three quarters soon after the middle of the month. It then begins to shorten, but does not go below an hour and one half until after the close of the month. Greatest east elongation (25° 29') is reached on June 27th. This is not quite the maximum possible, but is not much below it. The month of June this year therefore .hlronomical Soriely of the Pacifii . Hi gives about the best opportunity for naked-eye views of Mercury. Venus remains a morning star, rising i'' 20™ before sunrise on May 1st, and this interval remains about the same through- out the two-month period, even increasing a little toward the end of the period, although the apparent distance between planet and Sun is diminishing, the distance apart of the two bodies being 8° less at the end of the period than it was at the beginning. Although the planet is very low down until nearly the time of sunrise, its brightness is so great that there will be no difficulty in seeing it during the early twilight. Mars rises shortly before midnight on May ist, before jQh ^Qin o,, jujjg jst^ ^j,d before %^ 30" on June 30th. It moves eastward about 7° until June 5th. and from that time until the end of the month it moves westward about 4°. It remains in Sagittarius, north of the "milk-dipper" group. Its distance diminishes from sixty-nine millions of miles on May i.st. to fifty millions on June ist, and thirty-nine millions on June 30th. At the last dale its distance is only about one mil- lion miles greater than the minimum, which will be reached early in July. The planet will still gain materially in bright- ness all through the period, and will practically have attained its maximum at the end of June, it will then be about as bright as Jupiter. Mars will come to opposition on July 6th, and its nearest approach to the Earth will occur a few days later, the least distance being a little less than thirty-eight millions of miles. This is the most favorable opposition since that of 1892, which came on August ^d. The planet was then two and one-half millions of miles nearer the Earth than it will be om the last opposition to the present one the interval is 788 days, and the next period will be considerably longer. The cause is the eccentricity of Marss orbit, and the consequent variability in the velocity of the planet. Jupiter sets shortly before 11^ 30^ p.m. on May 1st. and shortly after 8** p.m. on June 30th. It moves eastward alxmt 13° in the constellation Gemini and at the close of the period is nearly due south of Castor and Pollux, the principal stars of the constellation. It is in conjunction with Mercury on June 15th, the latter passing 1° 41' to the north. Saturn is a morning object, rising somewhat less than two hours before sunrise on May ist, at 1** 26^ a.m. on June ist, and at 11^ 35*" p.m. on June 30th. It moves about 3*^ east- ward and 2° northward in the constellation Pisces, and at the end of June is only about 2° distant from the point marking the vernal equinox. The rings are practically out of sight during May and June, as the Earth and Sun are on opposite sides of the plane. Large telescopes may show the edge illu- minated, and possibly light may pass through small ga])s in the rings. A better opportunity for seeing the same i)henom- enon will come during the autumn, when Earth and Sun will have changed places relative to the rings. Uranus rises shortly before midnight on May ist, and shortly before 8'* p.m. on June 30th. It is still in the constel- lation Sagittarius and moves westward about 2° during the two months. It is in conjunction with Mars on May ist, which passes between it and the **milk-dipper" group at a distance of 0° 46' from Uranus. Neptune is in Gemini not far from Jupiter. The time of nearest approach is May 21st. Jupiter then passes 1^ north of Xeptune. (FIFTY-SIXTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Societv of the Paci fi<: has been awarded to Dr. A. Kopff, astronomer, Heidelberg. Astronomical Society of the Pacific. 83 Germany, for his discovery of an unexpected comet on August 22, 1906. J Committee of the Comet-Medal : W. W. Campbell, Chas. Burckhalter, San pRANasco, March 20, 1907. C. D. Perrine. (FIFTY-SEVENTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to Professor H. Thiele, astronomer, Copen- hagen, Denmark, for his discovery of an unexpected comet on November 20, 1906. Committee on the Comet-Medal : W. W. Campbell, Chas. Burckhalter, San pRANasco, March 20, 1907. C. D. Perrine. (FIFTY-EIGHTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to J. H. Metcalf, astronomer, Taunton, Massachusetts, for his discovery of an unexpected comet on November 14, 1906. Committee of the Comet-Medal : W. W. Campbell, Chas. Burckhalter, San Franosco, March 20, 1907. C. D. Perrine. LIBRARY NOTICE. Members who had in their possession at the time of the San r^rancisco fire any books or pamphlets belonging to the Library of the Astronomical Society of the Pacific are requested to send them to the Librarian ofrthe Society, R. T. Crawford, Students' Observatory, Berkeley, Cal. NOTES FROM PACIFIC COAST OBSEkVATORIES. Note on Comet Holmes. Search was made for Comet Holmes with the j;6-inch tele- scoiw on several nights before its rediscovery by pliotogrraphy by Professor Wolf, on August 28, 1906, and also on severa! nights in September. The conditions were fairly good, and an object as bright as 15th magnitude ought lo have been detected, but the comet was not seen, According to the corrections to Zwiers's ephemeris given by the photographic observations, the comet's place was cer- tainly examined, and it is therefore safe to conclude that its visual magnitude was below 15, Poor seeing on moonless nights in late October, when the comet reached its maximnm theoretical brightness, and in the following months, prevented further search. March, 1907. R. G. AlTKEN. A SiMi-LE Meti;ou of Computing the Le.\(tths ok Slexder I'neclipsed Solar Crescents. In a note on the contact thnes of the total solar eclipse of 1S08 Professor C.^.MPBELL called attention to the fact that the times as computed from the data of the different ephem- erides were not as consistent as might be wished, but in the case of that eclipse, as well as with earlier ones, there seems to be no evidence of a systematic variation of the observed from the computed times. For the eclipse of May 28, 1900. the preliminary report of the Lick Observatory-Crocker Eclipse Expedition to Georgia shows a difference of some seven or eight seconds between the computed and observed times of second contact. At tjje eclipse of August 30. 1903. the discrepancy was found to be greater. The Lick Obser\'a- tory party reported a difference of seventeen seconds for sec- ond contact and twenty-three for third, while other observers .ilso found that totality occurred about twenty seconds earlier /Istrottomtcal ooctety of the ractfic. 05 Ihan prctJicted. The difference is understood to be due to the increasing error of the Moon tables at present in use. To obtain a very approximate time for the beginning of totality' which shall be practically independent of tlie error of the lunar tables, the interval before the beginning of totality ihal ihe uneclipsed crescent of the Sun subtends a definite angle at Ihe Sun's center may be computed. A number of obserwTS have used this method, and Dr. Dowming has com- puted these data for the eclipse of January 3, 1908. In addi- tion to the times of contact computed in the ordinary way, he gives the limes before the commencement of totality cor- responding to cusp angles 90°, 60°, 45°, 30°. and 15 '. A note on the method used here in recomputing these values might not be without interest to eclipse observers. The ordinary eclipse fomiiilie give us the following: — d = Duration of totality. P.. and /*,, ^r: Points of contact II and Itl, with their position- angles from the E~\V line. Let «=; semi-diameter of Sun in seconds of arc, and h :^ semi-diameter of Moon in seconds of arc, corrected for aug- mentation. Draw the E-IV and N-S lines through O. tlie center of the Sun. Then, if C^ and C, are the positions of the Moon's center at contacts II and III, they will lie on P,0 produced and P, O produced, respectively, each at a distance b ^^ a seconds from O. \ line drawn through C, and C, will be the path of the Moon's center relative to 0. and the distance C.^ C^ will be traversed in d seconds of time. The velocity of the Moon's motion in seconds of arc per second of time is there- C C, fore _^ — - . This velocity is readily obtained, since in the triangle 0 CjC,, the sides O C, and 0 C, are known, and the angle at 0 is Ihe supplement of the sum of the posit ion -angles. Suppose the Moon's center at L when the semi-angle at the Sun's center subtending the arc joining the cusps of the un- eclipsed crescent is a. Draw L M and 0 M to one of the cusps, and also L O, which bisects the angle subtending the cusps, Krom the triangle L 0 M. L 0 may now be computed, hav- ing which, the triangle LC.j O is solved for L C,. TViU \s \.\\fc i distance over which the Moon's center must move before begin- ning of totality, and the velocity being known, the time is also determined. f- t. t. G. B. Blair. March, 1907. Incheased Water Supply on Mt. Hamilton. The following description of a new pumping plant at Mt. Hamilton is published for its possible interest to other moun- tain observatories. Up to the present time the Lick Observatory has obtained its water supply from a small spring (Aquarius) in the north canon, located about one mile northeast and 325 feet lower than the observatory buildings. The flow from this spring •exceeded the consumption in the late winter and early spring months and fell far short of the consumption in the summer and fall months. The storage and distributing reservoirs on Kepler Peak, one half mile east and fifty feet higher than the buildings, supphed the deficiency during the dry season. The . needs of the observatory for household and photographic pur- poses were met by this system, provided the rainfall for the year had been normal and constant care was taken to guard against leaks in the system. In seasons when the rainfall fell below the nonnal, it was necessary to use the water under short-allowance niles. This has occurred four or five times during the history of the observatory and has been a serious matter, especially as the system of fire protection was impaired just at the time of the year when it was most needed. Plans were formed two years ago to increase the water supply, based ujwn the use of a spring in the south canon, which is 300 feet lower than Aquarius, but whose flow is at least fifieenfold greater than that of .Aquarius. The system of pumping is a somewhat novel one, and I am under great obligations to Mr. J. A. Lighthipe, head of the Engineering Department of the General Electric Company in this district, for calling my attention to it. The spring is 680 feet lower than the Kepler reservoirs, and the distance between the two. measured on the thirty- degree slope, is 1.400 feet. Catchment reservoirs, capacity 12,000 gallons, have been established at the spring. A two- inch power and supply pipe leads from these reservoirs farther down the steep caiion. a distance of 700 feet on the slope, and ^Astronomical Society of the Pacific. 87 215 teet in altitude. At this lower level an hydraulic motor pump is installed. This is constructed very much liice an cnlinary steam pump, e.vcept that the steam cylinders are replaced by water cylinders, forming the motor. The pijie last described divides into two branches just above the pump. One of these connects with the motor end of the pump and the other with the pumping end. The piston areas for the two motor cylinders are sixfold greater than the areas of the pump- ing pistons. The large motor pistons, operated by six gallons of water with 215 feet head, enable the small pumping pistons to lift one gallon through the 2,100 feet of two-inch pipe to Ihe Kepler reservoirs. 895 feet in altitude above the pump. In other words, the pump places one gallon in seven in the Kep- ler reserx'oirs. the other six gallons doing the work. The sim- ple device of dividing the power pipe jnst above the pump so as (o supply water to the pump-end under a pressure of 215 feet, increases the efficiency of the pumping system to this extent. The only persona! attention required by the pump consists in filling the oil cups once a week. The pump was constructed by the Dow Pumping Engine Works, San Francisco, under the guarantee that it would do the work described. .\t the present time the pump is delivering 6,200 gallons per day to the Kepler reservoirs. Our average daily consump- tion throughout the year is about 1,700 gallons. It is expected that one gallon in seven during the late summer and fall months will deliver about 1,200 gallons per day. With the 200.000 gallons stored in the Kepler reservoirs, and with the Aquarius pumping system available in case of need, it is be- lieved that our annual anxiety as to the water supply will be eliminated. During the dry season the available water supply will be three- or fourfold greater than it has been in the past- .\n electric pumping plant is replacing the steam plant al Aquarius. .\It H.VMILTON, March 2;, IQ07, W. W. Campbell. Note on Comet a 1907 (Giacobim). The first comet of this year was discovered close to opposi- tion. March gth. by Giacobint. at Nice. From the first three available observations (March 9th, by Giacobini, at Nice-, March iitb. by Rice, at Washington; March I2t\\, b^ Y\t«., Publirntions of the al Mt. liamiiton) a preliminary orbit was computed. The elements and cphemeris are given in Lick Observatory Bulle- tin, No. III. Dr. AiTKKN states that "the comet as seen here on the first date was very small, round, with well-marked condensation, and almost equal to an eleventh -magnitude star in brightness." It is now receding from the Earth. The observations are satisfied by a parabola. The comet has a retrograde motion, the plane of its orbit having an inclination of 142° to the ecliptic. Its nearest approach to the Sun was on March 12th, at which time it was 190.000.000 miles, or 2.05 astronomical units from it. The longitude of perihelion is 50° ; the longitude of the ascending node is gfi°. Having no later observations from the East, and not having one from Mt. Hamilton because of the position of the Moon and the continual rain in California, it has been so far impos- sible to obtain a second orbit. Sivy^v^a Ein'arson-. F-STKl.I.E GlANCV. Bebkelev A5Tso^■l)^f rc.M, Depahtment, March 27. 1907. ^^B Nf>TK ON CosiiiT b ir^io6 (Kopi^f). ^H This comet was discovered in March, 1906, by Kopff. at Heidelberg. Its geocentric motion was very small. From a t\venty- two-day arc a set of parabolic elements was computed by Mr. Champbku.v and myself and published with an ephcm- eris in Lick Obscnvlory Bulletin, No. 97. The remarkable feature of the orbit is the great perihelion distance, 3.3 astro- nomical units. Because of it.'* great distance from the Sun its heliocentric motion in the last year has been but 50*^, The Earth has therefore overtaken the comet, and it was picked up again March 21st nf this year by Kopff. The residuals for this place from our orbit are (O-C) Ao^^ — o''.6; AS^ + o°.i. a change of about eight days in the time of perihelion passage will remove the greatest part of these. No attempt will be made to improve these elements on the basis of this year's observation since Professor Weiss has found and published in .4. jV, 4154 a set of elements and ephemeris which represent this place almost exactly. Weiss's elements have been deduced from observations extending from January, /yoj. to iMay, 1906. The pos\UoT\ of January, 1905, is from a Astronomical Society of the Pacific. 89 photographic plate by Professor Wolf, found after the comet had been discovered by Kopff. More than 800 days have elapsed since this observation of January, 1905, so that, ex- cepting the periodic comets, this comet holds the record for length of time during which it has been under observation. It is further highly probable that it will be picked up when the Earth overtakes it again next year. Russell Tracy Crawford. Bfjikeley Astronomical Dkpartment, March 30, 1907. The Promotion of Dr. Aitken. It gives me great pleasure to announce that Dr. R. G. Aitken has been promoted to the position of Astronomer in the Lick Observatory. It is unnecessary to say that this action on the part of the President and Regents of the University '\^ thoroughly deserved. It would be difficult to speak too highly of Dr. Aitken's scientific researches. His work on double stars is certainly unsurpassed in quantity, quality, system, and breadth of view. ,,, ,,, ^ W. W. Campbell. Promotion of Professor Leuschner. The promotion of Dr. A. O. Leuschner, Director of the Students' Observatory, from Associate Professor to Professor of Astronomy is another well-earned event which it gives us pleasure to record. Professor Leuschner has built up one of the strongest and best of astronomical schools ; and although his teaching, and administrative duties both inside and out- side of his department, have been heavy, he has found time to make valuable investigations and to encourage and direct similar investigations by the assistants in his department. The publication of Professor Leuschner's work on the Wat- son asteroids is awaited with interest. W. W. Campbell. REPORTS OF OBSERVATORIES.' CHAMBERMN OUSERVATORY, DENVER, COLORADO. The work of the Cliamberlin Observatory during 1906 was confined to observations of comets, the installation of some new apparatus, and some sjiecial studies in personal equation. H. A. Howe, Director, INTERNATIONAL LATITUDE OBSERVATORY, UKIAH, C The programme of the International Geodetic Association for observing variations of latitude was changed at the begin- ning of igo6 by dropping the twenty-four refraction pairs (pairs which culminate at large zenith-distances, about 60°). and also six of the latitude pairs, and substituting for these new latitude pairs. The observing-list now consists of ninety- six pairs, distributed throughout the twenty-four hours of right ascension, sixty-six of which belong to the old list and thirty of which are new. All of the stars culminate at zenith- distances of less than 26°. Observations continued throughout 1906 without serious interruption from any cause. The weather was favorable during all months except February. March, and December, a monthly total of less than 150 pairs being considered unfavor- able. The three longest intervals without observations were fourteen nights in August, eight nights in January, and six nights in each of February, November, and December. The first of these was caused by the absence of the observer and the others by unfavorable weather. The rainfall for the year was 51.8 inches. The maximum temperature was 108" P., on July 24th; the minimum temperature 22°, on November 24th. 28th, 29th. The following table gives a summary of the observations made for the variation of latitude. The first column contains the number of determinations made each month, the second col- umn the number of nights upon which observations were made, the third column the number of complete nights (sixteen de- terminations), the fourth column the greatest interval in each month during which no observations were obtained. Astronomical Society of the Pacific. 91 1906. Pairs. Nights. Nights. Nights. January 175 13 8 8 February 1 14 10 5 6 March 138 11 7 5 April 203 14 II 5 May 180 13 9 5 June 220 18 12 3 July 247 16 IS 5 August 224 14 14 14 September 263 17 16 3 October 238 17 14 4 November 212 15 11 6 December 144 12 7 6 Totals 2,358 170 129 Means 196.5 14 1 1 6 Definitive reductions of all the observations for the varia- tion of latitude (233) obtained between April 4th and May 4th, both inclusive, were made in order to determine if possible whether or not there was an appreciable shift in the Earth's crust at Ukiah at the time of the earthquake of April i8th. No sudden change in the latitude was found. The results of the computations were printed in these Publications (vol. XVIII, p. 241). Sidney D. Townley, Astronomer-in-Charge, LICK observatory, MT. HAMILTON, CALIFORNIA. The scientific work of the Lick Observatory during the calendar year 1906 was pursued by each member of the staflf with his accustomed industry and enthusiasm. It related for the most part to advancing the solution of the greater problems upon which we have been engaged in past years, and only here and there were minor or new problems taken up. Professor Tucker, with the aid of Mr. R. F. Sanford, Carnegie Assistant, has completed the extensive reductions of his meridian-circle observations of 2,800 zodiacal stars, and the manuscript results are nearly ready for publication. The pur- pose of these observations is to provide more accurate ref- erence-points in the zodiac as a basis for securing improved orbits of the planets. Mr. Tucker continued throughout the year the observation of a carefully constructed programme of stars, for the purpose Publications of the of scciiriiij; a system of star places of llie highest accuracy, which shall be strictly fintdameiital. as opposed to basing ob- servations upon a system established with other instalments. There is need in these observations for the most accurate clock that can be secured, and a Ricfller constant-pressure clock, with nickel-steel pendulum, was installed late in 1906. .-V special list of stars, used by Professor DooLiTTLii:, of the University of Pennsylvania, in a sluiiy of terrestrial latitude variations, has also been observed by Mr. Tucker. Out of 965 photographs of the minor planet Eros, made at the favorable opposition of i<)oo. 525 have been selected as a basis for improving our knowledge of the Sun's distance from the Earth. Excellent progress in the measurement and reduc- tion of these photographs has been made by Miss Cii.\se and Miss HoDE. Carnegie Assistants, under the supervision of Dr. Perrine. Another year should see the work well along toward completion. There will be nothing of special interest to com- municate to general readers until all the measures are combined in a final solution for the most probable value of the Sims distance. Good progress has been made in the study of the eclipse photographs of 1905, obtained by the Crocker Expeditions to Spain and Egypt. Mr. Perrine has made a careful examination of the photo- graphs secured in Spain and Egypt for the in tramercu rial- planet search. The Spanish plates record stars in the region examined down to about the eighth photographic magnitude, but all of the images observed on the plates have been identified as those of well-known stars, .-\ssuming that the planet would be one magnitude fainter photographically than visually, the search may be .said to prove that no planet as bright as the seventh magnitude exist.s within the region searched. This in- cludes an area about 9° by 29° lying along the direction of the Sun's equator. It will be remembered that similar search made at the Sumatra eclipse of 1901 by Mr. Perrine was limited in one third of the area to stars brighter than the sixth photographic magnitude. The Spanish results are thus an extension and advance of those secured in Sumatra. It is becoming more apparent that the anomalous motion of Mercury's perihelion must seek an explanation elsewhere than in the attractions of Astronomical Sorii'ty of the Pacific. 93 intraniercurial planets. A paper piiblisliert very recently hy Pro- fessor SEii:L[<;ER makes it extremely probable that the hitherto unexplained anomalies in the motions of the four inner planets arc due to the attractions of the widely distributed materials responsible for the zodiacal light. It is unfortunate that clouds limited the observations in Sumatra and Spain. The cameras employed are capable of recording tenth-magnitude stars with clear skies and exposures of three minutes or less. It is hoped that an eclipse of the near future will enable this limit to be reached and thus give completeness to the observational pro- gramme. The unusually favorable eclipse of 1905 afforded a hope that large-scale photographs of the corona secured in Labrador, Spain, and Egypt, or in two of these countries, would enable tis to detect changes in the coronal structure occurring between the instants of totality in those countries. Dr. Pf.hkike and I have made careful comparisons of the photographs secured in Spain and Egypt. A number of well-defined nuclei existed both east and west of the Sun. Details of structure within the nuclei suffered change, but the masses as a whole appeared to remain in fixed positions. We are able to say that those masses could not have moved so much as one mile per second during the interval of seventy minutes which elapsed between the totalities in Spain and Egypt, Greater speeds might well have occurred in the principal coronal streamers without our having detected them : for their stnicturc is uniform and regu- lar, and well-defined nuclei are absent. Thus, in the cases where high speeds should perhaps be most expected, the photo- granhic method has little power to detect them. In connection with the Sumatra eclipse, Mr. Pkrrine was able to reach the interesting conclusion that a large disturbed volume of the corona, conical in form, apjieared to be situated exactly over the large and only sun-spot visible during several days preceding and following the eclipse. A very similar disturbed volume is shown on the coronal photographs of 1905. The vertex of the cone does not appear to be over one of the large spots then existing on the Sun. but it is above a large region of the photosphere which shows many signs of dis- turbance. The complete reduction of the time and longitude observa- tions in Spain confirms definitely the conclusion reached on 94 Publications of the eclipse day, — that mid- totality occurred twetity seconds earlier than the time predicted by the nautical almanacs. It is hoped that the spectrograph ic and poiarigraphic results will be ready for publication within the coming year. The D. O. Mills Expedition to Chile terminated its first period of activity on March i, 1906. At that time Dr. Curtis assumed charge for the second period of five years, in succes- sion to Professor Wright, who returned to California shortly thereafter. The working programme of the original ex]>edi- tion called for s])ectrograms of all the brighter stars south of declination - — 25° which should contain lines capable of accu- rate measurement, down to photographic magnitude 5.5. The stars so selected formed a list of 143. Four spectrograms were obtained of practically every star on the list, and additional ones of many others were taken for special pur[>oses. Eight hundred spectrograms in all were obtained. The half of these were definitively measured and reduced by January, 1907, and it is expected that the results from the other plates will be ready by the middle of the present calendar year. I am inclined to ascribe great imjwrtance to this programme of work, now nearing completion in accordance with plans which have been definitely held in mind since 1894. There is a tremendous demand for the knowledge of the velocities of the stars determined spectrographically, for use (a) in deter- mining the motion of the solar system as a whole, and (fe) in determining the structure of the sidereal universe. Observa- tions of this kind either have been made or are under way at ten northern-hemisphere observatories. The southern two sevenths of the sky. out of reach of northern instruments, nnist be observed in the same manner before a satisfactory soUition of these problems can be hoped for, and before the observations of the northern stars can assume their fuU value. Up to 1906 existing southern-hemisphere observatories have published spectrographic velocities of but two or three stars. The Mills Expedition was organized to secure observations of the brighter stars with special reference to their use in prob- lem a. In the erection of the observatory on Cerro San Cristobal, Santiago, during the rainy season, in meeting and overcoming difficulties as they arose, and in carrying out the programme of observation as planned within the estimated time. Acting- ' Astronomical Society of the Pacific. 95 Astronomer William H, Wsight, in charge of the expedi- tion, is entitled to great credit. The dearth of southern -hemisphere observations of the exact Icinds that tlie Mills Observatory is fitted to supply made it extremely desirable that our station should continue in active existence. When the subject was presented to Mr. Mills, he was pleased to provide for its liberal support through a further period of five years, and for many improvements and addi- tions to the instrumental equipment. Dr. Ct'HTis, in charge of the expedition during its second term, is assisted by Mr. GEORdE Paddock, formerly of the University of Virginia. The determinations of the radial velocities of the stars on Mt. Hamilton by means of the Mills spectrograph attached to the 36-inch equatorial made good progress during the year igo6. About 400 spectrograms were secured, principally by Messrs. Campbell. Moohe, and Wright. The stars observed were, on the average, fainter than in former years. This in- volved longer exposures, and resulted in a slightly reduced number. A considerably larger number of spectrograms taken in igo6 and former years were measured and reduced defini- tively, principally by Messrs. Moohe, Burns, and Newkirk. Profes.sor Aitken's programme of double-star observations with the 12-inch and 36-inch refractors has two main pur- poses; (fl) to examine systematically all the stars to the ninth magnitude inclusive between the North Pole and — 22° of declination, checking the positions of all previously known double stars and noting all additional pairs that are under five seconds in distance, as the basts for a thorough statistical study of double stars; and (t) to measure regularly all known double stars showing motions of revolution, especially the more rapid and diffiailt pairs, to provide data for improving our knowledge of their orbits. Approximately, 300 new pairs were (iiscovi;red in the year. Seventy-five per cent of them are under two seconds of arc. This work involved careful examination of 10,000 stars, in round numbers. The total number of new stars discovered by Messrs. Aitken and Hussey, who co-operated in organiz- ing and prosecuting this double-star survey, is about 2,900. Given reasonably good winter skies, the programme for the northern hemisphere should be completed by Dr. Aitken within three years. i The second part ol Dr. Aitkrm's programme is tlioroiighly systematized, so that observations of tlie more rapid and dif- ficult pairs are obtained at the times most advantageous for determining their orbits. A considerable number of micrometer observations of the comets of igo6 have been made by Messrs. Aitkkx, Maddhill, Smith, and Fatu. A large number of photographs of Jupiter's sixth and seventh satellites have been obtained by Dr. Perrine with the Crosstey reflector for the purpose of improving our knowl- edge of their orbits. Photograjihs of Salunt's ninth satellite and Xcpiunc's satellite have also been secured. Extensive experimental work with reference to future investigations with this instrument have also been conducted by Dr. Perrine. Very extensive observations of several well-known variable stars have been made with the one-prism spectrograph by Messrs. Alurecht and M-adobill, as a basis for theses, in partial fulfillment of requirements for the degree of Doctor of Philosophy. In all cases these variables have been shown to be spectroscopic binaries, and iheir accurate observations will be of great value in the efforts that arc constantly being made to determine why these and other stars of their class vary in brightness. Mr. Mahiirill has given special attention also to the pho- tometry of several variable .'itars with a view to detennining possible relationship.-; between peculiarities in their brightness- and velocity-curves. His photometric results are of very satisfactory accuracy, A fruitful investigation has been made by Dr. Alurecht on the relation of the effective wave-lengths of blended spec- tral lines and stellar s[5ectra of different types. He has shown that the effective wave-lengths of many blends change pro- gressively with the spectral type. A long list of minor investigations and results should for completeness be mentioned, but space is tacking. The observatory has abundant cause for thanksgiving in that the great earthquake of April iSth did very little damage. Reference may be made to an article on this subject in an earlier number of these Publications. The D. O. Mills Ob- servatory. Chile, had its corresponding ex[)ericnce only four months later, and was equally fortunate. Let us hope that Astronomical Society of the Pacific. 97 tUese trials, so closely cunnccted in lime and Riving rise to so rniicJi anxiety, were but a horrible coincidence, and that they may not reair for many generations. Tlie installation of an important electric plant for lighting and power purposes began in May, under the difficult condi- tions of supply, labor, and finance induced by the earthquake and fire, li should be completed early in the year 1907. An automatic pumping plant, installed at the same time, is in operation, and promises to increase the water supply three- or fourfold, with little expense. Acknowledgments are due to the Regents of the University t>f California, to Mr. D. O. Mills, to Mr. W. H. Crockf.h, and to the Carnegie Institution for generous financial support, and to all the members of the Observatory Staff for their enthusiastic and efficient aid in carrying out the scientific '''^'^- W. W. Camprell. Director, LOWKLL 0[!SER\ATORV. FLAOSTAFF. ARIZONA. During the first part of the year the large telescope was em- ploj-ed in spectrographic work, the charting of star-fields with the Brashear photographic doublet and micrometric observa- tions. Since July the doublet has been mounted on the 6-incli Clark refractor, and the time of the large telescope has been devoted, for the greater part, to spectrographic observations. During the sununer and autumn further experiments in plane- tary photography were carried on. Mr. Si.ipher's programme of spectrographic work has con- sisted principally of line-of-sight observations of stars. Mod- ification of parts of the large three-prism spectrograph were made by Bhashgar in January. February, and March. The changes made, remounting of the prisms and providing tiie collimator with a curved slit, have proved very satisfactory, and have added much to the efficiency of the instrument. Ob- servations were made with the three-prism sijectrograph until the middle of August. During the autumn months spectro- graphic observations of the fainter stars were made with the single- prism spectrograph. The original mounting for the simple prism which made use of the spectrometer section of Ihc large spectrograph, lacked stability for long exposures. Rut after modification of this part, from designs by Mr. i Publications of the Slipher, no trace of flexure has been found for exposure of as much as four hours' duration on the one side of the meridian. In the single-prism instrument one of the dense flint prisms of the prism -train of the large sjjectrograph has been used. This prism gives a dispersion of 35 tenth-meters per miUime- ter at Hy. By tipping the plate the camera is made to give a sharp focus over the range of spectrum comi>rised Ijetwecn K and A 4600, over whicli region tlie measures are commonly extended. In the course of this work several stars have been found to have variable radial velocity, and the spectrum of t Capricomi has been found to contain bright lines. Though the measurement of the plates is much in arrears, the results thus far obtained indicate a large field of work for this form of instrument. Of the spectra of variable stars photographed with the single-prism instrument the most interesting is per- haps that of Mira Ceti, secured at the recent iiniisiially bright maximum of this star during December and Januarj'. One spectrogram was made with the three-prism instrument. With the improved sensitizing dyes now available, giving a fairly even deposit over the entire range of sensitiveness of the plate, it was possible to photograph the spectrum with the single- prism instrument from below B to H8, All the hydrogen lines covered by the plate are bright. ( See note in the Astrophys- ical Journal for January. I'jo?, and the reproduction of one of the plates of the spectnmi in the March number of that publi cation.) In connection with the spectrographic work. Mr. Slipher has experimented further with sensitizing dyes, par- ticularly those active for the less refrangible end of the spec- trum, for the application of such to photographic investigation of absorption bands in planetary spectra and also for work on the lower end of stellar spectra, with the result that plates more sensitive to the red can now be prepared. The greater rapidity and more perfect gradation of these plates than of those for- merly available makes it possible to extend the study of the spectra of planets and stars considerably farther into the red. A great many star-fields have been photographed with the Brashear doublet during the year. This lens was at first car- ried on the 24-inch refractor. When the mounting of the 6-inch Oark refractor was completed, in July, the doublet wa^ mounted on it. and since then the time of this instrument has been devoted wholly to photography. This work was done Astronomical Society of the Pacific. 99 until June by Mr. J. C. Duncan, Lawrence Fellow at this observatory for 1905-1906. Since July the work has been continued by Mr. E. C. Slipher, fellow for the present year. In addition to making photographs of star-fields and the series of photographs of Comet c 1905, Mr. Duncan made micrometric measures for position of Comets c 1905, a and b 1906. In view of the approaching favorable opposition of Mars, further experiments in planetary photography have been car- ried on by Mr. Lampland. It is hoped that the greater bright- ness and larger disk of the planet, together with such improve- ment as may be expected from past experience and more suit- able and efficient apparatus, will bring still better results than were obtained in 1905. For the present, at least, the greatest value of the results obtained by photography is the evidence the negative brings to corroborate data obtained visually. The great mass of observational data and the results deduced there- from, accumulated since Schiaparelli*s epoch-making obser- vations were begun, have been obscured and distorted more or less by unfounded skepticism, based on the idea that many of the observed phenomena are subjective effects or spurious products of observation. The questions raised have been thoroughly investigated from the standpoint of theory and ex- periment and found untenable. With the further confirmation of the visual results by photography, it seems that there should be no room for doubt in the matter. ^ -. Percival Lowell. naval observatory, mare island, CALIFORNIA. As indicated in the last annual report, this observatory was established mainly for keeping up the public time service for the Pacific Coast, and for the rating of chronometers used in the naval service. During the past year the work has been maintained as usual. At the time of the great earthquake the time-signals were sent out the following day, but the Western Union Telegraph Company's lines wd-e so deranged and congested with busi- ness that the signals could not always be delivered. Yet even during this trying period they managed to deliver the signals about every second day, which was sufficient for commercial purposes. The earthquake stopped two of the four clocks of the observatory, and deranged the time of tiie other two by more than twenty seconds. The pendulums rubbed against the index ledges, and this with the shocks affected the rates of motion. The earthquake was carefully observed here, and a full re- port has been submitted to the State Earthquake Commission. After this terrible disaster to the State, the theory of earth- quakes ordinarily adopted seemed so improbable and so inca- pable of explaining the observed phenomena tliat a general survey of the subject was attempted, in the hope of gaining a better understanding of the cause of such disturbances. The results of this investigation have just been puMished in the Proceedings of the American Philosophical Society at Phila- delphia. It is shown that the main cause of great earthquakes is the expulsion of lava from under the bed of the sea. by the explosive power of steam, which forms beneath the Earth's crust, owing to the secular leakage of the ocean bottoms. Another investigation is about finished which deals with the problem of the secular cooling of the Earth and the theory of contraction, so generally adopted in the physical sciences. The results obtained are not without interest to investigators. A new Riefler clock, moving in an air-tight case, has just been installed in the observatory, and it promises to perform with great perfection, and will thus afford additional accuracy to the time service in the winter season, when long spells of cloudy weather arc common. T T I Spp Professor of Mathemalics, U. S. N., in charge of the Observatory^^M SOLAR onSEHVATORY OF THE CARNF.GIR INSTITUTION OF'^1 VV.^SHTNfiTON. MT. WILSON. CALIFORNIA. The most important event of the year, so far as its bearing on the future of the observatory is concerned, was the gift of $45,000 by Mr. Jons D. 1-[ookf;r, to meet the cost of a mirror of one hundred inches aperture for a great reflecting telescope. The difficulties in the way of constnicting and using success- fully a mirror of this size have been outlined elsewhere. It is sufficient to say here that the mirror is certain to give results of great importance in those classes of work where the finest definition is not essential, while there is good reason to hope Astronomical Society of the Pacific. loi that for the direct photography of nebulae, and for other inves- tigations requiring even more perfect definition, there will be some nights in the year in which the full advantages of the large aperture will be realized. The glass disk has been ordered from the plate-glass works at St. Gobain, France, and work has been undertaken on the fireproof structure in which the grind- ing and polishing of the mirror will be done by Professor RiTCHEY. The work of research has included : 1. Daily photography of the Sun with the photoheliograph ; 2. Daily photography of the Sun with the spectroheliograph ; 3. Photography of the spectra of sun-spots; 4. Photography of the flocculi, for the determination of the radial velocity of the calcium vapor ; 5. Spectrographic investigations of the solar rotation; 6. Bolographic investigations of the solar absorption; 7. Special studies of stellar spectra with a spectrograph of high dispersion; 8. Laboratory investigations; 9. Preliminary studies of the correlation of solar and mag- netic phenomena. The 5-foot spectroheliograph was erected in the Snow tele- scope-house in October, 1905. It has given admirable results from the outset, the daily records including photographs of the Sun with the calcium, hydrogen, and iron lines. These photo- graphs have been studied in various ways, the principal routine investigation in which they are employed being a determination of the solar rotation. The daily motions of the calcium flocculi required for this purpose are measured by Miss Ware, with the "heliomicrometer," an instrument which permits the latitude and longitude of points on a photograph of the Sun to be measured directly, without computation. This instrument was constructed in the observatory shop and has been thoroughly tested during the year. Measures can be made with it as rapidly as with ordinary measuring-machines, and apparently with no less precision. A comparative study of the hydrogen and calcium flocculi indicates that the former He at a somewhat higher level in the solar atmosphere. Stereoscopic comparisons of calcium photo- I02 Publications of the graphs taken at intervals ranging from one to ten hours have also proved very instructive. Much time has been devoted to the study of the spectra of sun-spots, for the purpose of interpreting the cause of the strengthening and weakening of solar lines. The photographs of spot spectra used for this work were taken by Mr. Adams and Mr. Ellerman with the i8-foot Littrow spectrograph, used in conjunction with the Snow telescope. These photo- graphs show thousands of lines not previously recorded, and have served admirably for present investigations. For the in- terpretation of the changes in the relative intensities of the lines, many laboratory experiments were made by Dr. Gale. It was soon found that by varying the temperature of a metallic vapor, such as iron or titanium, the changes in the relative intensities of the lines observed in sun-spots could be closely imitated. This work, carried out systematically, led to the conclusion that the characteristic line intensities of spot spectra are probably the result of the reduced temperature of the spot vapors, as compared with those of the ordinary reversing layer. This conclusion was confirmed by the discovery in spot spectra of the flutings of titanium, which do not appear to be present at the higher temperature of regions outside of spots. A study of the spectrum of Arcturus, photographed with a spectrograph of very high dispersion, showed that the lines that are strengthened in sun-spots are in general strengthened in this star, at least in the region investigated. Lines that are weakened in sun-spots also appear to be weakened in A retu- rns. This is a natural result if we assume a spot to be a com- paratively cool region on the Sun, and if we suppose Arcttirus to be a star like the Sun, cooled to a temperature of the same order as that of sun-spots. The presence of titanium flutings in third-type stars affords another close bond of connection between these stars and sun-spots. Results of this character, when followed up with the aid of the 6o-inch reflector, should throw much light on the temperature classification of stars. The radial motion of the calcium vapor in the flocculi has been studied spectrographically by Mr. Adams. The average displacement of the H^ and K.^ lines corresponds to a velocity of approach of the calcium vapor amounting to about 0.41*™ per second. The varying displacements obtained at different times, however, indicate that general conclusions should be Astronomical Society of the Pacific. 103 based only on very extensive investigations. The results given by the bright lines Hg and K^ also show a displacement toward the violet, so that the calcium vapor in the flocculi may be regarded as moving upward. Mr. Adams is engaged on an extensive study of the solar rotation, based upon comparative photographs of the spectra of opposite limbs, made with the 18-foot spectrograph of the Snow telescope. The results, so far as reduced, are very consistent, and should prove to be an important contribution to this subject. Holographic studies of the absorption of the solar atmos- phere, made by Dr. Palmer, with the advice and co-operation of Mr. Abbot, seem to indicate that the absorption may fluctu- ate in an irregular manner within short periods. No satisfac- tory conclusions can be drawn, however, until the investigation has been carried farther and correlated with simultaneous studies of the solar constant. Professor E. F. Nichols, of Columbia University, carried on two special investigations during the summer. One of these was the study of the effect of the ionization produced by X-rays upon the absorption or radiation of a gas or vapor. The second investigation dealt with the question whether the "Reststrahlen" obtained after repeated reflections from rock-salt surfaces reach us in any appreciable amount from the Sun. The latitude and longitude of the Solar Observatory were determined by Messrs. Smith and McGrath, of the U. S. Coast Survey. The results obtained are as follows: — Mt Wilson Triangulation Station. Snow Telescope Pier. Latitude 34° 12' 59"72 34'' 12' 59".53 Longitude 118 3 45 -54 118 3 34 .89 The Smithsonian Institution sent a second expedition to Mt Wilson during the summer of 1906, for the purpose of con- tinuing the work undertaken in 1905. Although the season was hardly as satisfactory as the previous one, a large number of determinations of the solar constant were obtained. These are of a high order of precision, and should leave no doubt, when reduced, of the character of the variations which the results of 1905 seemed to exhibit. The admirable methods developed by Mr. Abbot, in conjunction with the late Secretary Langley, I04 Publications of the seem well calculated to clear np the long-standing question as to the variability of the solar radiation. The work of the Computing Division has been organized and placed under the direction of Mr. Adams. A series of offices added to our building in Pasadena provide suitable quarters for this work. Three computers, Miss Ware, Miss Lasby, and Miss Smith, are at present employed. Miss Ware, as already stated, is engaged in the measurement of solar photographs with the "heliomicrometer." Miss Lasby is measuring Mr. Adams's photographs of spectra taken for the determination of the solar rotation. Miss Smith is measuring the area of the calcium flocculi, in regions ten degrees square on the solar surface, for the purpose of ascertaining the distribution and va- riation of the solar activity. Special apparatus, devised for this purpose, was constructed in the observatory instrument-shop. The work of the Construction Division has made admirable progress under the direction of Professor Ritchey. Work has advanced on the 6o-inch mirror and its mounting, the heavy parts of which were received from the Union Iron Works in the autumn. In addition, many smaller instalments have been constructed. The five-ton automobile truck, to be used for transporting the mounting of the large reflector and the steel for the building and dome in which it is to stand to the summit of the mountain, has also arrived in Pasadena. The work of widening the "New Trail" into a road is well advanced and will be completed in the spring. This work has been carried out under the immediate superintendence of Mr. Godfrey Sykes, of the Desert Botanical Laboratory of the Carnegie Institu- * tion, acting under the general direction and with the active co-operation of Professor Ritchey. Further details of the work of the year may be found in the Annual Report of the Director, in Year Book No. 5 of the Carnegie Institution, and in Contributions front the Solar Ob- servatory, Nos. 3 to 14. ^ T- TT n- ^ •^ "^ ^ George E. Hale, Director . students' observatory, BERKELEY ASTRONOMICAL DEPART- MENT, UNIVERSITY OF CALIFORNIA. The year ending December last has been notable for a marked increase in enrollment in the courses offered by the Berkeley Astronomical Department. The number of students Astronomical Society of the Pacific. 105 during tlie fall term of the year 1906 was 216, the same as the combined enrollment for the two preceding terms. With the enrollment during the current tenn, the attendance for the academic year ( 1906-1907) has reached 378, as against 216 for the preceding year. The staff of the department has devoted practically all of its time to instruction and has had to forego the much-desired completion of several astronomical investigations. The depart- ment was further seriously handicapped during the fall term by a prolonged illness of Mr. Einarson, the assistant. Nevertheless, the regular computation by the **Short Method" of one or more preliminary orbits of all newly discovered comets was continued during the year, with the exception of one case, by Dr. Crawford, generally with, the assistance of graduate students. In his capacity as member and secretary of the State Earth- quake Investigation Commission, the Director has devoted much time to the collection and systematizing of data on the California earthquake of April i8th. On July I, 1906, Dr. Crawford was promoted to be Assist- ant Professor of Practical Astronomy. Important additions to the instrumental equipment have not been made. The observatory has been fortunate, however, in having the use of an Omori tronometer belonging to the Im- perial Earthquake Investigation Commission of Japan. With the aid of this instrument numerous good records of after shocks have been secured, as well as records of three earth- quakes at a distance, including the Valparaiso earthquake in August. The work on the Watson asteroids has progressed sufficiently to make it certain that the tables of twelve asteroids reported on a year ago will go to press in April. The chief assistant in this work has been Miss Estelle Glancy, Dr. Newkirk having accepted a position as Carnegie Research Assistant at the Lick Observatory in September. Dr. Crawford's further investigation of the constant of refraction, and Dr. New kirk's tables for the reduction of measured photographic positions and his investigation of the Repsold measuring-engine are to be published in April. A. O. Leuschner, Director, GENERAL NOTES. The Work of the Harvard College Obsen'atory. — From Pro- fessor E. C. Pickering's report for the year ending September 30, 1906, it appears that the work of the Harvard College Observatory continues to be mainly the quantitative and qual- itative analyses by visual and photographic methods of the light of the stars. By means of photometers attached to the east equatorial at Cambridge, and of the meridian photometers at Cambridge and at Arequipa, many thousands of measures have been made during the year of the brightness of stars, with the object (a) of. extending to stars of the thirteenth magni- tude the plan of furnishing standards of magnitude on a unifonn scale well distributed over the entire sky. and (b) of increasing our knowledge of the variable stars, especially of those of long period and of those of the Algol type. Miscella- neous photometric measures include the photometric measures of twenty-nine eclipses of Jupiter's satellites. A large number of photographs, including spectrum plates. have been taken with the ir-inch and 8-inch Draper telescopes at Cambridge, and with the 8-inch Bache, the 13-inch Boyden, and the 24-inch Bruce telescope at Arequipa. The study of these plates has already revealed many new variable stars, stars with bright hydrogen lines, etc. Other plates have been utilized to extend the classification of stellar spectra to fainter stars on the plan of the classification given in volume XXVIII of the Annals. The great majority of the plates are neces- sarily stored for future study. Professor Pickehing again calls attention to the urgent need of the observatory of suitable fireproof buildings for housing the admirable library of the observatory, one of the finest astronomical libraries in the world, for the photographic laboratory, and for a workshop. A still greater desideratum is an addition to the staff of assistants. As Professor Picker- ing says, "Perhaps the greatest return could be obtained by the employment of more assistants for the study of the unique collection of astronomical photographs. This collection now contains 189,200 photographs of the stars, and is like a library of that size with only about twenty readers." Astronomical Society of the Pacific. 107 An Interesting Variable. — The leading article in the Astro- nomische Nachrichten, No. 4148, by G. Muller and P. Kempf, gives the determination of the period and the light-curve of a new short-period variable of the h Cephei type. The star is located in the constellation Cassiopeia, B. D. 68° 200, and has an average brightness of a little less than the sixth magnitude. Its period was found to be 1.9498 days. But the chief interest lies in the smallness of the range of brightness ; this was found to be only 0.33 of a magnitude. Observations were made photometrically by both of the authors, and in order to be certain that the variations found were in reality not large accidental errors of observation they requested a third observ- er, Mr. K. Graff, of Hamburg, to make visual observations upon the star by Argelander's method, without, however, giving him any exact knowledge of the period to be expected. The observations of Mr. Graff completely confirmed those obtained at Potsdam, and there seems to be no doubt about the reality of the variation. When it becomes possible to dif- ferentiate with certainty a variation of a quarter of a magni- tude from the accidental errors of observation, it serves to illustrate the degree of precision attainable in modern photo- metric work. An Unknoivn Comet. — During 1905 Professor E. E. Barnard, of the Yerkes Observatory, was stationed for a time at the Solar Observatory of the Carnegie Institution on Mt. Wilson, in California, engaged in photographing the south- em portions of the Milky Way with the Bruce photographic telescope of the Yerkes Observatory. After returning from the expedition a re-examination of the plates disclosed the trail of a very faint comet on each of three plates taken on July 22, 1905. These plates have been measured by Professor Barnard, giving an accurate position of the object, and the results have been published in the Astronomische Nachrichten, No. 4153. The comet had a right ascension of between eight- een and nineteen hours and a declination between 20° and 21° south. So far as known, it was neither seen visually by any one nor photographed at any other place. The chief interest in the object lies in the possibility of its belonging to the class of periodic comets. If such should be the case, and it should be observed at some future return to the neighborhood of the io8 Publications of the Earth, the position determined by Mr. Barnard might prove very valuable in fixing its orbit. Heights of Meteors. — Under the title, "Heights of Large Meteors Observed in 1906/' {Astronomische Nachrichten, No. 4152,) W. F. Denning gives some interesting results obtained from the observations of ten meteors in England by himself and persons co-operating with him. The height at appearance varies between fifty-nine and eighty-nine miles, with an aver- age value of seventy miles ; the height at disappearance varies between twenty-two and fifty-six miles, with an average value of forty miles; the length of path varies between twenty-four and seventy-two miles, with an average of forty-four miles; the velocity in miles per second (given for only six) varies between fifteen and thirty, with an average value of twenty- two. It would be interesting if some one could devise a means of computing, or even roughly estimating, the mass which must be possessed by a meteor in order that it may give forth light during its flight through a certain stretch of the upper atmos- phere at a given velocity. Isaac Roberts's Celestial Photographs. — Mrs. Dorothea Isaac-Roberts has published in the Astronomische Nach- richten, No. 4154, a "Preliminary Catalogue of Isaac Rorerts's Collection of Photographs of Celestial Objects." This collec- tion consists of 2,485 original negatives of stars, star-clusters, nebulae, and other celestial objects, together with many posi- tives on glass and on paper. Over half of the negatives were taken with a 20-inch reflector of ninety-eight inches focal length, and the balance were taken with various lenses up to five inches in diameter. Mrs. Roberts proposes to make this fine collection of nega- tives available for the advancement of astronomical science, as may be seen from the following quotation from her article: — " As soon as circumstances permit, a complete list of Isaac Roberts's tribute to astronomy will be published, in accordance with the wishes and instructions of the deceased. ** The number of copies of the forthcoming paper being very limited, the observatories and astronomers, official or amateur, who are specially interested in photographic astronomy will please send in their names to the address given below, early in 1907, in order that Astronomical Society of the Pacific. 109 the various parts of the complete catalogue may be sent to them in course of time. " Positives-on-glass reproduced from the Isaac Roberts negatives will be lent for the purpose of micrometric measurements, if appli- cation be made, and provided that the documents be returned after completion of the measurements." Mrs. Roberts's address is Chateau Rosa Bonheur, By- Thomery, Seine et Marne, France. Ncii' Asteroids, — The number of asteroids now exceeds six hundred. Dr. J. Bauschinger, Director des Astronomisches Rechen-Instituf, Berlin, has recently printed, in the Astro- nomische Nachrichten, No. 4156, sets of elements for twenty- five of these small bodies discovered during 1905 and 1906. The Monthly Notices of the Royal Astronomical Society for December. 1906, contains an article by Professor H. H. Turner, "On the Possibility of Improving the Places of Ref- erence-Stars for the Astrographic Catalogue from the Photo- graphic Measures," which is characterized by the simplicity of method and evident practical value which mark his other contributions on the subject of photographic measures. In the process of the reduction of the measured rectangular co- ordinates of star-images on a photographic plate to the right ascension and declination of the corresponding stars, plate constants are derived with the help of the images of stars whose positions are known from meridian or other independent observations. The unavoidable errors in the positions of these stars of reference affect the plate constants and through them the positions of the previously unknown stars which result from the measures. It is the readjustment of the assumed co-ordinates of the stars of reference by a comparison of the measures of their images made on overlapping plates that is treated in this paper. In the Oxford reductions for the astrographic catalogue it has been customary to substitute for the least-square solution of the equations for the plate constants a method in which all the equations are combined to form eight derived ones, four of which involve the constants a, h, c, and the remaining four the constants d, e, f. The four derived equations of each group are obtained by adding the equations arising from the no Publications of the star-images in the four quadrants of the plate respective! Each of the four derived equations of one group may be regarded as arising from a single fictitious star, its weight being equal to the number of stars in its quadrant. Mr. Turner shows that if the four equations are of equal weight, and if the four fictitious stars are in the center of their respective quadrants, the four residuals after solution, either by his method or by the method of least squares, are -f- 1, — I, + I, — - 1, respectively, where I is the algebraic sum of the absolute terms of the four equations, two of them taken with the opposite sign. This quantity I is called the "incon- sistency" for the plate. It will be zero in the assumed case if the co-ordinates of the comparison-stars are correct, and the measures are affected by no errors that are not linear func- tions of the measured co-ordinates. Where the actual state of affairs is not too unsymmetrical it is possible therefore to write down the residuals before the solution is made and to determine, without a solution of the equations, how the resid- uals would be affected by arbitrary changes in the co-ordinates of the comparison-stars, — that is, in the absolute terms of the equations of condition. Ft would be entirely possible to make the inconsistency for a single plate zero without improving the plate constants, but any changes that materially reduce the inconsistencies of a series of overlapping plates would un- doubtedly improve the plate constants of all of them. Professor Turner has not arrived at any general and entirely satisfactory method of accomplishing this adjustment, but the tabulation of the inconsistencies of a series of overlapping plates in "diagrammatic" form will undoubtedly lead to such adjustments, provided the symmetry of arrangement of the comparison -stars is sufficient to render applicable his theorem regarding the residuals. The Gold Medal of ihe Royal Astronomical Society Azvarded to Professor E. \V. Broziti. — The gold medal of the Royal Astronomical Society has this year been awarded to Professor Ernest William Brown for his "Researches in the Lunar Theory." On presenting the medal to Professor Brown at the annual meeting of the society, February 8, 1907, the president, Mr. WiLLi.^M H. M.^w, reviewed the work of the distinguished Astronomical Society of the Pacific. in medalist in an able and comprehensive address, from which the following is taken. Professor Brown is the seventh astronomer to whom the gold medal of the Royal Astronomical Society has been awarded for work in connection with the lunar theory. In a paper entitled "Theory of the Motion of the Moon, Containing a New Calculation of the Expressions for the Co- ordinates for the Moon in Terms of the Time," published in volume LI II of the Memoirs, he has clearly stated the nature of the problem on which he has been engaged, in the following words : — " The formation of numerical expressions deduced as a consequence of the Newtonian laws of motion and gravitation which shall represent the position of the Moon at any time may be roughly divided into three stages. As a first step, we consider each of the three bodies — the Sun, the Earth, and the Moon — as a sphere of mass equal to its actual mass, and arranged in concentric layers of equal density. The Earth (or center of mass of the E^rth and Moon) is supposed to move round the Sun in a certain ideal elliptic orbit, and all disturbances of this orbit and of the Moon from any other source than the ideal Sun and Earth are neglected. The first stage constitutes nearly the whole of the problem of three bodies as far as the particular configuration of the Sun- Earth- Moon system is concerned. When this is done, we pro- ceed to the second step, which involves the determination of the effects due to the difference between the actual and the ideal motions of the Earth and Sun, to the influence exercised by the other bodies of the solar system, and to the differences between the real and ideal arrangements of the masses of the bodies. The calculations so far may, theoretically at least, be made without any knowledge of the configuration of the system at any given time or times, beyond a general idea of the order of mapiitude of certain of the constants involved. The third and final stage consists in a determination by observation of the various constants which have entered into the theory and the substitution of their values, so as to obtain numerical expres- sions for the co-ordinates in terms of the time." It is the completion of the first of these stages which has primarily been the object of Professor Brown's past labors; and as a result he has, after arduous work extending over the past fifteen years, completed the solution of the problem of three bodies for the case of Sun-Earth-Moon with an accuracy very far in excess of that attained by any of his predecessors in this line of research. Dr. G. W. Hill, who speaks with the highest authority, has expressed the following opinion on Professor Brown's work : — Publications of the " Much as we rightly welcome the results of Professor Brown's devoted labors, wc should be unwarranted in assuming thai their en*- plopnent in the lunar tables would give rise to a marked improvement in llie representation of observations. A slight one indeed might be expected; but it has been evident for some time that the Moon deviated from its calculated orbit more because it is subject to irregular forces, which we have not yet the ineanii of estimating, than because the tables are affected by slight defects in the mathematical treatment of the forces which are already recognised. This circumstance in no sense diminishes the credit due to Professor Brown's work." By giving accurate values to the known perturbations. Pro- fessor Brown has defined more clearly the further irregulari- ties of whit:h the explanation has yet to he ascertained. The precautions taken by the medalist to secure accuracy in the final results have been most refined. In accordance with the original programme, every coefficient in longitude, lati- tude, and parallax which is so great as one hundredth of a second of arc. has been computed, and is regarded as accurate to at least this amount, the results being obtained to one thousandth of a second. To avoid the occurrence of errors of computation, e(|uations of verification have been computed at every step of the work, every page of the manuscript having, on the average, not less than two test equations computed. The medalist is the first lunar theorist to use independent equations of verification, thus creating a higher degree of confidence in his results than could ever come from mere duplicate calculation. In devising the details of his research, the medalist arranged the work so that considerable proportions could be done by computers; but as a matter of fact only one — Mr. Ira L. Stehseb, of Haverford College, of whose ability and accuracy Professor Brown speaks in the highest terms — has been em- ployed. "The calculations have probably occupied altogetfier eight or nine thousand hours. There were about 13,000 multi- plications of series made, containing some 400,000 separate products ; the whole of the work required the writing of between some four or five millions of digits and plus and minus signs." Professor Brown has completed his solution of the prob- lem of three bodies for the case of the Sun -Earth-Moon by methods involving striking elegance and originality, and show- ing great powers of resource. He has. however, by no means Astronomical Society of the Pacific. 113 finished his labors. As he himself has pointed out, in announc- ing the completion of the main problem, much still remained to be done before it was advisable to proceed to the construc- tion of tables. On this work he is now engaged, and we may rest assured that he will continue to bring to bear upon it that energy and power of organized inquiry which have enabled him already to secure such brilliant results. Professor Brown is an Englishman who has long been resident in America, and who has for the past sixteen years been connected with Haverford College. That association will, however, be broken in the ensuing summer, and next autumn Professor Brown proceeds to Yale University. It is exceed- ingly gratifying to know that his work on the lunar theory, which he has been able to carry on at Haverford under most favorable conditions, will not be interrupted by this change. The Yale authorities have recognized the importance of his work by arranging special facilities for its continuance, and have also most generously undertaken to provide the funds required for both the preparation and publication of the lunar tables which will form the natural outcome of Professor Brown's labors. A. O. L. \^oIume I, number I, of the Journal of the Royal Astronom- ical Society of Canada bears the date January-February, 1907. The object of the society is, in the words of the editor, **to extend and popularize the study of astronomy, astrophysics, and related branches of science." The pages of the journal are to be open to accounts of the work of amateurs as well as to technical papers. For the present the publication is to appear bi-monthly. The editors hope, however, soon to be able to issue it monthly. Among the papers of especial interest in this first number may be mentioned the president's address, on "Progress in Astronomy and Astrophysics during 1906," and an article by J. S. Plaskett, on "The Spectrum of Mira Ceti." The "Notes from the Dominion Observatory," "Brief Astronomical Re- views," and "Astronomical News" are also worthy of mention as interesting and valuable features. Notes from ^'Science" — A bill has been introduced in the legislature incorporating the New York Observatory and Nau- 114 Publications of the tical Museum, to which reference has already been made in Science, It is stated in the charter that this museum is "for the purpose of encouraging and developing the maritime in- terests of New York City, of advancing the general knowl- edge of the safe navigation of the sea, of the development of harbor facilities, of prosecuting original researches in astron- omy and navigation and in kindred subjects, and of affording instruction in the same." Substantially, the museum would be placed on the same basis as the Museum of Natural History and the Metropolitan Museum of Art. The city is to provide the land and is to erect the buildings, while the corporation is to secure by private subscription not less than $300,000 for equipping the nautical museum and observatory and for prosecuting the other objects of the institution. The French Government has made Professor Simon New- comb, U. S. N., (retired), Commander of the Legion of Honor. Mr. E. B. McClellan, third assistant at the RadcliflFe Ob- servatory, Oxford, died on January 2d, at the age of forty-five years. » Mr. H. F. Newall, of Trinity College, Cambridge, assistant director of the observatory, has been elected president of the Royal Astronomical Society, in succession to Mr. W. H. Maw. Planet Markings. — At the 628th meeting of the Philosoph- ical Society of Washington, held on P>bniary 2d, Professor Newcomb read a paper on "The Optical and Psychological Principles Involved in the Interpretation of the Markings on the Disks of the Planets." A short outline of the paper may be found in Science for March i, 1907. Mr. James D. Maddrill, of the University of California, Fellow in the Lick Observatory, who will take the examinations for the degree of Doctor of Philosophy in Astronomy, Physics, and Mathematics in May, has been appointed by the Superin- tendent of the United States Coast and Geodetic Survey to succeed Dr. Sidney D. Town ley as observer at the Interna- tional Latitude Observatory in Ukiah, and will enter upon his duties in July. .A. O. L. Astronomical Society of the Pacific. 115 Obituary. — The Astronomische Nachrichten, No. 4i45» con- tains a notice concerning the life and works of Jean Abraham Chretien Oudemans, who died on December 14, 1906, at the age of seventy-nine years. Oudemans was for many years Professor of Astronomy and Director of the Observatory at the University of Utrecht. He was chiefly interested in the practical side of astronomy, and as an observer and computer held high rank among his contemporaries. He was also inter- ested in geodetic work, and spent eighteen years in charge of the triangulation of the Dutch East Indies. The result of this work was published in six volumes under the title of "Trian- gulation of Java." Although Professor Oudemans retired from the directorship of the Utrecht Observatory in 1898, yet he did not give up his astronomical work, and only a short time before his death presented a paper at a meeting of the Royal Academy of Sciences of Amsterdam, on the "Mutual Occultations and Eclipses of the Satellites of Jupiter in 1908," an abstract of which will be found in these notes in our next number. Miss Acnes Mary Clerke, the scientific writer, died on Sunday morning, January 20th, at her residence, 68 Redcliffe Square, S. W., London, England, at the age of sixty-four. An astronomical correspondent writes with reference to Miss Clerke : — " During the last century two ladies only were elected honorary members of the Royal Astronomical Society — Caroline Herschel and Mrs. SoMERViLLE. The new century soon saw fresh honorary members elected, and among them Miss Agnes Clerke, whose last important work, * Problems in Astrophysics,' was of such great scientific value that the Astronomical Society could no longer ignore her claims to public recognition by them. And when we say ' last important work ' we must acknowledge also the outstanding merit of two earlier books, 'The System of the Stars' and 'History of Astronomy in the Nine- teenth Century,' besides less important volumes, 'The Herschels and Modem Astronomy,* * Modern Cosmogonies/ and many scientific mag- azine articles, principally of the nature of reviews or interpretations of results, in which her keen insight into the true significance of ob- served physical facts was as wonderful as her fluency and command of language, so that both from the literary and scientific standpoints she must be ranked as a great scientific writer. No one writing a history of modern astronomy can fail to acknowledge the great debt owed to the masterly array of facts in her ' History.' No worker in the vast field of modern sidereal astronomy" opened by the genius of Herschel and greatly widened by the application of the spectroscope Ii6 Publications of the Astronomical Society, &c. to the chemical and physical problems of the universe lacked due recognition by Miss Clerke, who performed as it seemed no other writer could have done the work of collation and interpretation of this enormous mass of new material, ever pointing the way to new fields of investigation, often by one pregnant suggestion sweeping aside a whole sheaf of tentative conjectures and indicating, if not the true line — for in many cases the truth is yet to seek — at least, a plaus- ible and scientific line well worth pursuing. She will be missed at the meetings of the Royal Astronomical Society, at which she was a constant visitor even before her election as an honorary member, and where her clear judgment was at times called upon to determine the value of some new suggestion in the domain of celestial physics. She was not a practical astronomer in the ordinary sense; but her death, on Sunday morning, leaves a gap that will be hard to fill. She was the daughter of Mr. John William Clerke, who died in London in 1890. Her sister. Miss C. M. Clerke, who died a few months ago, also wrote on astronomical subjects, though in a far more humble way." — The Times, Loudon. NEW PUBLICATIONS. Belopolsky, a. Untersuchung der Ca-Linien am Sonnen- rande. Mitteilungen der Nikolai-Haupt Sternwarte zu Pulkowo. Band I, No. 12. 1907. 4to. 23 pp. JJoNSDORFF, I. Beobachtiingen von 3 Cassiopija* mit deni grossen Zenitteleskop. Mitteilungen der Nikolai-Haupt Sternwarte zu Pulkowo. Band II, No. 13. 1907. 4to. 16 pp. Canxon, Annie J. Second catalogue of variable stars. Cam- bridge : Annals of the Astronomical Observatory of Har- vard College. Vol. LV, Part I. 1907. 4to. iii + 94 pp. Paper. CooKSON, Bryan. Determination of the mass of Jupiter and orbits of the satellites from observations made with the Cape heliometer. Edinburgh: Annals of the Royal Ob- servatory, Cape of Good Hope. Vol. XII, Part II. 1906. 4to. 215 pp. Paper. 6s. DE Sitter, W. A determination of the inclinations and nodes of the orbits of Jupiter's satellites, from photographic plates taken at the Royal Observatory, Cape of Good Hope. Edinburgh: Annals of the Royal Observatory, Cape of Good Hope. Vol. XII, Part III. 1906. 4to. 139 pp. Paper. 4s. Franz, J. Der Mond. Leipzig: Teubner. 1906. i2mo. 132 pp. Halm, Jacob. New reduction of Henderson's catalogue for the epoch 1840.0. Glasgow : Annals of the Royal Observ- atory, Edinburgh. Vol. II. 1906. 4to. xl + 104 pp. Cloth. 6s. Ujui), ]•*. H. Notes on the computation of logarithms. Colo- rado Springs: Semi-annual Bulletin of the Colorado College Observatory. 1907. 8vo. 19 pp. r^UNT, Joseph. The spectra of silicon, fluorine, and oxygen. Edinburgh: Annals of the Royal Observatory, Cape of Good Hope. Vol. X, Part II — Spectroscopic Researches. 1906. 4to. 43 pp. Paper. 3s. Ii8 Publications of the MuLLER, G., und Kempf, P. Photometrische Durchmusterung des Nordlichen Hinimels, enthaltend die Groszen und Far- ben aller Sterne der B. D. bis zur Grosze 7.5. General- katolog. Potsdam : Publikationen des Astrophysikalischen Observatoriums zu Potsdam. Band XVII. 1907. 4to. XXXV -f- 293 pp. Boards. i8m. OuDEMANS, J. A. C. Mutual occultations and eclipses of the satellites of Jupiter in 1908. Parts I and II. Reprinted from the Proceedings of the Amsterdam Academy of Sci- ences, 1906. 32 and 15 pp. Weinek, L. Astronomische Beobachtungen an der K. K. Sternwarte zu Prag. in den Jahren 1900-1904. Prag. 1907. 4to. vi + 106 pp. Plates. Wood, R. W. Physical optics. New York: Macmillan Co. 1907. 8vo. 546 pp. Qoth, $3.50. Positions of Phoebe, 1898-1904. Cambridge: Annals of the Astronomical Observatory of Harvard College. Vol. LX, No. III. 4to. 40 pp. Paper. Eclipses of /M/>i7^f^.y satellites, 1878-1903. Cambridge: Annals of the Astronomical Observatory of Harvard College. Vol. LII, Part I. 4to. iii -|- 148 pp. Paper. The Nautical Almanac for 1910. Edinburgh: 1906. 8vo. xiii -|- ^2 4- 44 pp. Paper, 2s 6d. Catalogue of stars for the equinox 1900.0, from observations made at the Royal Observatory, Cape of Good Hope, dur- ing the years 1900- 1904. Edinburgh: 1906. 4to. xiii -f- 123 pp. Cloth, 4s 6d. A catalogue of 8,560 astrographic standard stars between declinations — 40° and — 52° for the equinox 1900.0, from observations made at the Royal Observatory, Cape of Good Hope, during the years 1896- 1899 (with three ap- pendices). Edinburgh. 1906. 4to. lix -f- 403 pp. Cloth. Results of meridian observations of stars made at the Royal Observatory, Cape of Good Hope, in the years 1900 to 1904. Edinburgh. 1906. 4to. xxx -f- 274 pp. Qoth. Astronomical and niagnetical and meteorlogical observations made at the Royal Observatory, Greenwich, in the year 1904. Edinburgh. 1906. 4to. cxlvi -f- (334) + (P^) + 1 55 + 97 + /^'"* + (cxliii) -f 9 -f 23 +vii + 24 pp. Cloth. Astronomical Society of the Pacific. 119 MlNUTESU)F THE MEETING OF THE BOARD OF DIRECTORS HELD ON March 30, 1907, at 7 : 30 p.m. President Leuschner presided. A quorum was present. The following resolution was adopted: — Resolved. That the Publication Committee be authorized to expend $600 for Publications to the end of the current calendar year. Adjourned. ' Minutes of the Nineteenth Annual Meeting of the Astronomical Society of the Pacific, held in the Law Offices of Gushing, Grant & Gushing, 1652 OTarrell Street, March 30, 1907, at 8 p.m. The meeting was called to order by President Leuschner. A quorum was present. The minutes of the last meeting were approved. The Committee on Nominations reported a list of names proposed for election as Directors and Committee on Publication. Messrs. Baird and Cornish were appointed as tellers. The polls were open from 8: 15 to 9 p.m., and the following persons were duly elected to serve for the ensuing year : — For Directors: R. G. Aitken, A. H. Babcock, Chas. Burckhalter, Wm. H. Crocker, W. W. Campbell, Chas. S. Cushing, George E. Hale, S. D. Townlev, F. R. Ziel, R. T. Crawford, D. S. Richardson. For Committee on Publication: R. G. Aitken, S. D. Townley, B. L. New KIRK. REPORT OF the DONOHOE COMET-MEDAL COMMITTEE FOR THE YEAR I906. The following comets were discovered during the year 1906: — Comet a 1906, an unexpected comet, was discovered by Professor W. R. Brooks at Geneva, New York, on January a6th. Comet b 1900, an unexpected comet, was discovered by Dr. A. Kopff at Heidel- berg, Germany, on March 3d. Comet c 1906. an unexpected comet, was discovered by D. Ross at Melbourne, Australia, on March 17th. Comet d 1906, Fiklay's periodic comet, was re-discovered by Dr. A. Kopff at Heidelberg, Germany, on July i6th. Comet e 1906, an unexpected comet, was discovered by Dr. A. Kopff at Heidel- berg, Germany, on August sad. Comet / 1906, Holmes's periodic comet, was re-discovered by Professor Max Wolf at Heidelberg, Germany, on August 28th. Comet g 1906, an unexpected comet, was discovered by Professor H. Thiele at Copenhagen, Denmark, on November loth. Comet h 1906, an unexpected comet, was discovered by Rev. J. H. Metcalf at Taunton, Massachusetts, on November 14th. The Donohoe Comet-Medal of the Astronomical Society of the Pacific has been awarded to the discoverers of Comets a, b, c, e, g, and A. It should be noted that Comets b, d, e, f, and h 1906 were discovered by photo- graphic methods. Respectfully submitted, W. W. Campbell, Chas. Burckhalter, V Committee. C. D. Perrine, ■■) I20 Publications of the The Treasurer submitted his Annual Report, as follows : — Annual Statement of the Receipts and Expenditures of the Astronomical Society of the Pacific for the Fisc\l Year Ending March 30, 1907. GENERAL FUND. Receipts. 1906. April 1st. Balance $ 36 11 Received from — Dues for 1906 and previous years $191 05 Dues for 1907 555 40 $ 746 45 Life membership fee 50 uo Sales of Publications 39 00 Legacy, Estate of Morris Reiman 500 00 Less inheritance tax $18 90 Less lawyer's fees 50 00 68 90 431 10 Life Membership Fund (interest) 72 04 Life Membership Fund (loan) 276 25 John Dolbeer Fund (interest) 219 47 Wm. Alvord Fund (interest) 180 84 London & Lancashire Fire Insurance Company, for loss under Policy No. 4823220, on claim of $2,000 i>9oo 00 $3.9x5 15 $3,951 26 Less transfer to Life Membership Fund (fee) $ 50 00 Less transfer to Montgomery Library Fund (fire insurance loss) 1*900 00 1,950 00 $2,001 26 Expenditures. For Publications — Printing Nos. 106 to 112 $1,115 75 Illustrations 9 10 $1,124 85 Reprints '. $36 50 Stationery and printing 71 20 Postages ^ . 60 00 Rent .. .. Salary Secretary-Treasurer 180 00 Expressages Janitor Gas Insurance premiums Fee re claim vs. Rhine-Moscllc Fire Insurance Co.. Lantern at lecture Engrossing Notary fees Rent safe deposit box Hank exchanges 18 71 11 90 20 17 60 s 00 8 00 2 ^5 3 50 5 00 30 420 16 1.545 01 1907. March 30th. Italnucc $ 456 25 Dues outstanding — For 1 906 $ 1 00 00 For 1 907 31000 $410 00 Astronomical S^ociety of the Pacific. * 121 LIFE MEMBERSHIP FUND. 1906. April ist. Balance $i.953 9S Received from General Fund (fee) 50 00 Interest 72 04 $2,075 99 Less transfer to General Fund (interest) $ 72 04 I^ss transfer to General Fund (loan) 276 25 348 29 1907. March 30th. Balance $1,727 70 ALEXANDER MONTGOMERY LIBRARY FUND. 1906. April ist. Balance $1.53387 Received from London & Lancashire Fire Insurance Company, on claim of $2,000 i ,900 00 Interest 67 50 • 1907. March 30th. Balance $3>50i ^7 DONOHOK COMET-MEDAL FUND. 1906. April I St. Balance $ 766 57 Interest 28 94 $ 795 51 I^ss engraving medals Nos. 53, 54, 55, and postage 2 85 1907. March 30th. Balance $ 792 66 BRUCE MEDAL FUND. 1906. April ist. Balance $2,66904 Interest 122 61 1907. March 30th. Balance $2,791 65 JOHN DOLBEER FUND. 1906. April ist. Balance $5,000 00 Interest 219 47 $5,219 47 Less interest expended for Publications (see Oneral Fund).... 219 47 1907. March 30th. Balance $5,000 00 WILLIAM ALVORD FUND. 1906. April ist. Balance $5,000 00 Interest « . . . . 180 84 $5,180 84 I.CSS interest expended for Publications (see General Fund).... 180 84 1907. March 30th. Balance $5,000 00 122 Publications of the Balances as follows: — General Fund, With Donoboe-Kelly Banking Company $ 45625 Life Membership Fund. With German Savin^^s & Loan Society $ 727 70 South Pacific Coast Railway Co. ist Mortgage 4 per cent guaranteed (by S. P. Co.) $1,000, Gold Bond No. 3406 1,000 00 (Interest Jan. and July; principal due July i, 1937.) 1,727 70 Alexander Montgomery Library Fund. With Security Savings Bank $i,377 35 Oakland Transit Consolidated, 1st consolidated Mortgage^ 5* per cent, $1,000 Ck>ld Bond No. 4328 1*040 00 (Interest Jan. and July; principal due July i, 1932.) Sunset Telephone and Telegraph Company, consolidated Mortgage 5 per cent, $1,000 Gold Bond No. 641 1,084 02 (Interest April and Oct.; principal due Oct. i, 1929.) 3,501 37 Donohoe Comet-Medal Fund. With San Francisco Savings Union 792 66 Bruce Medal Fund. With Mutual Savings Bank $ 801 93 Bay Counties Power Company, ist consolidated Mortgage 5 per cent, $1,000 Sinking Fund Gold Bond No. 1636.. 1,012 50 (Interest March and Sept. ; principal due Sept. i, 1930.) The Edison Electric Company, Los Angeles, ist and Re- funding Mortgage 5 per cent, $1,000 Gold Bond No. 168 977 22 (Interest March and Sept.; principal due Sept. x, 1922.) 2.791 65 John Dolbeer Fund. With Union Trust Company $ 970 28 South Pacific Coast Railway Company, ist Mortgage ^ per cent guaranteed (by S. P. Co.), $1,000 Gold Bond No. 3407 1 ,000 00 (Interest Jan. and July; principal due July 1, 1937.) Oakland Transit Consolidated, ist consolidated Mortgage 5 per cent, $1,000 Gold Bond* No. 4329 1.040 00 (Interest Jan. and July; principal due July i, 1932.) Bay Counties Power Company, 1st consolidated Mortgage S per cent, $1,000 Sinking Fund Gold Bond No. 1637. 1,012 50 (Interest March and Sept. ; principal due Sept. i, i93f>.) The Edison Electric Company, Los Angeles, ist and Re- funding Mortgage 5 per cent, $1,000 Gold Bond No. 169 977 22 (Interest March and Sept.; principal due Sept. i. 1922.) 5.000 00 William Alvord Fund. With Humboldt Savings Bank $ 331 94 With Savings & Loan Society 1,463 50 Sunset Telephone and Telegraph Company, consolidated Mortgage 5 per cent, $1,000 Gold Bond No. 656, and $1,000 Gold Bond No. 657 2,168 06 (Interest April and Oct.; principal due Oct. i, 1929.) Contra Costa Water Company. 5 per cent $1,000 Gold Bond No. 87 1 ,036 50 (Interest Jan. and July: principal due Jan. i. 19x5.) — i^— — 5,000 00 San Francisco. March 30, 1907. - Examined and found correct. _ Charles S. Cushing, "4 Auditing B. A. Baird, f Committee. F. R. ZiEL, Treasurer. The report was, on motion, accepted and filed. Astronomical Society of the Pacific. 123 The President, in an informal address, briefly reviewed the condition of the Society, and then proceeded to speak on the results of statistics on the eccentricities of comet orbits, an extract of which appears in this number of the Publications. Professor Aitken gave an interesting talk on "Double Stars." The thanks of the Society were returned to Messrs. Gushing, Grant & Gushing, for the use of their rooms. Adjourned. Minutes of the Meeting of the Board of Directors held March 30, 1907, at 10 p.m. The new Board of Directors was called to order by President Leuschner. a quorum was present. The minutes of the last meetinjji: were approved. The business in hand being the election of officers for the ensuing year, the following officers, having received a majority of the votes cast, were duly elected: — President: Mr. Ghas. S Gushing. First Vice-President: Mr. A. H. Babcock. Second Vice-President: Mr. W. W. Ga.mpbell. Third Vice-President: Mr. Geo. E. Hale. Secretary: Mr. R. T. Grawford. Treasurer: Mr. F. R. Ziel. Committee on the Comet-Medal: Messrs. W. W. Gampbell {ex officio), Ghas. Burckhalter, G. D. Perrine. Library Committee: Messrs. Grawford, Irving, Townlev. Mr. Grawford was appointed Librarian. The President was authorized to appoint the members of the Finance Gommittee^ and made the following selections: — Finance Committee: D. S. Richardson (Ghairman), Wm. H. Grocker, Ghas. Burckhaltfji. The Committee on Publication is composed of Messrs. R. G. Aitken. S. D. Town LEY, B. L. Newkirk. The following resolution was adopted : — Wherea.s, Mr. F. R. Ziel retires from the office of Secretary of the Society after fifteen consecutive years of service; Resolved, That the Directors hereby express their hearty thanks to Mr. Ziel for the disinterested fidelity and the great efficiency of his services to the Society. Adjourned. 124 Piih/ications of the ^Astronomical Society, &c. OFFICERS OF THB SOaSTV. Mr. Chai. S. Ci'iuiira PmUtnt Mr. A. H. Baicock Firn Vict-eraidnl Mr. W. W. Caiipiell Stcand Vict-PrtMtiU Mr. Gko E. Hali Third VietPrtsiitM Mr. R. T. CitAWraiD (Sludcnli' Ohiervalory. Berkeley) Stcrflary Mr. F. R. ZlEi Board tif Diririori — Mcssra. Aitkin, Babcdck. Bu«ciiHAi.iEit, Cauphll. Cuscee*, C«AWfO>D, CUSHIHG, HaII, RiCHAUltOH, TowSLEY. Z.tl.. Financi Cammitltt—Httsn. Ricbauson, Ceockei, Bu»ckh*lie«. CommilUi en PublicalioK — Meun. Aitken. Towhlev, Newiibi:. Cemmiltte oa Ihr Comet-Mrdni — Meuri. Campbell (ex-official. PEBIIHE. NOTICE. The atlention ot new memlKn is called to Article VIII of the By-Liwa, ofaich provides thai Ihe innual subscTiption, paid on election, covera Ihe calendar jax only. Subiequenl onngal narmenla are due on JanuaTy ist of each aucceedini calendar year. This rule is n«e««ary in order to make our bookkeeping ■> timple ■■ poiiible. Duet Knt b* mail (liould be directed to Aitroooinical Society af the Pacinc, So6 Franklin Street. Sao Francisco. It im intended that each member of the Society ihall receive a copy of each one of Ibe Publicalioni for tbe year in which he wai elected lo memberlhip and for all lubKqueut years. If there have be the stock in hand is sufBcieni, on ihc. paynenl of two dollara per volume to either of the Secretaries. Any non-mident member within the United States can obtain books from the Societr's library hr' sending his library card with ten cents in stamps to the Secretary A. S. P., Students- Ubservalory, Berkeley. Cal., who wUI return the book and tbe card. way, those napcra are printed Rrst which are earliest acceptcl (or tniblieatioiL Papers intended to be printed in a given number of Ihe PiblicMiont should be in author* whose residence is not within the United Slates. The responsibili^ for tbe with the writers, and Lliol assumed by The S°aciety itself. The titles of papers for reading should be communicated lo either of Ihe Se»- reUries an early as possible, as well as any changes in addresses. The Secreurf SUmped with Ihe seal of Ihe 5aciely. at cost price, as follows: a block of letter paper. 40 cents; of note paper, 15 cents; a package of envelope!, is cents. ThEM prices include postage, and should be remitted by money^rder or in U. 5. poaUcr Ttmse members who propose to attend tbe meetings at Mount Hamilton durinl the summer should communicate with "The Secretary Aitronomical Society of the Pacific." Students' (Observatory, Betkeley, Cal., in order thai ar PUBLICATIOSS ISSUED BI-MONTHLY. IFfbmary. April. June, ffiigiiil, Octabtr, Dictmbtr.'. I I I ■ ■* ". I «• yi i- \\ I ; . ■ rt 4.4* . » ■ ' PUBLICATIONS \ ..--^ ^ OK THE ' - —■'•'• Astronomical Society of the Pacific. Vol. XIX. San Francisco, California, June 10, 1907. No. 114. ECLIPSKS AND TRANSIT.S OF THE SATELLITES (.^F SATURX OCCURRING IX THE YEAR 1907. By Hkrman'n Stri've. In the present year the cycle of eclipses and transits of the satellites of Safnni extends over all satellites, inchidinjT; Titan, and it is to be ho|)ed that this very favorable oj^portunity of observing these interesting^ phenomena will not be lost. I have therefore computed the a])proximate times and ])laces of the eclipses and transits for every day from June 20, 1907, to January 17, igo8. In the following tables are first collected the data for the eclipses and transits of Titan, phenomena which can be observed also with smaller instruments. It wouM be of jvir- ticular interest to observe the eclipses of Titan with jihotom- eters, the long duration of the ap])caranccs of Titan i^'w'uv^ sufficient time for photometric comparisons. In the casL* of Titan it happens that both phenomena, the disa])pearance and the reappearance, are visible on the same day from the Earth. The times given for the eclipses of Titan are the moments when the center of the satellite passes the shadc^w-cone from the center of the Sun. For the transits of the shadow and of the disk of Titan the times of their crossinLC the minor axis of the planet are computed, and also the semi-duration of the transits, giving the approximate times of their ingress an. the geocentric place of the satellite at the lime of his eclipse, — i. e. the dis- tance of the satellite from the limb of the planet, and the posit ion -angle, counted from the north point of the minor axis of the disk. The duration of the appearances, occurring this year nearly centrally, may be, in the case of Rhea several minutes, iu the case of Tctliys and Dione about one minute, in the case of Mimas and Enccladiis only a few seconds. The attention of astronomers who are in possession of powerful instruments is particularly directed to these phenomena. On account of the disapjjea ranee of the rings before July aCith and after (_>ctober 4th, and of their minuteness in the interval between those dates, it seems however very likely that in tliis year also instruments of moderate size can take part in these interesting observations. It would be of great value also to ascertain the times of disappearance and reappearance of the rings by watching the planet carefully some days before and after the predicted dates. The observation of the first disappearance, on April 17th, will escape on account of the nearness of the Sun, but the reap- pearances of July 26th and January 7th and the disappearance of October 4th can be well observed. Finally are added the approximate Greenwich times, when the shadows of the satellites Tethys, Dione, Rhea cross the minor axis of the disk, together with their distances from the center of the disk at the time of conjunction. In the present opposition HyPerion also will be eclipsed at the times of his superior conjunction; but as it is doubtful whether these eclipses can be observed with sufficient accuracy I have not thought it worth while to calailate their times. In the preparation of the following tables I was kindly as- sisted by Dr. P. GuTHEKlcK. Royal Observatory. Beslin, Mnrch. igo?. >Sm thcK PublicaUoni. Vnl. XVIII. p. joj Astronomical Society of the Pacific. 127 DISAPPEARANCE AND REAPPEARANCE OF THE RINGS OF SATURN. 1907. April 17. Disappearance. The Earth in the plane of the rings. July 26. Reappearance. The Sun in the plane of the rings. October 4. Disappearance. The Earth in the plane of the rings. 1908. January 7. Reappearance. The Earth in the plane of the rings. ECLIPSE8 OF TITAN. s and p denote the geocentric place of Titan at the time of its eclipse, i. e. the distance from the limb of the planet, and the position-angle, counted from the north point of the minor axis to the west or to the east. 1907. June 7 Disapp. June 7 Reapp. June 23 Disapp. June 23 Reapp. July 8 Disapp. July 9 Reapp. July 24 Disapp. July 25 Reapp. Aug. 9 Disapp. Aug. 25 Disapp. Sept. 10 Disapp. Sept. 27 Reapp. Oct. 13 Reapp. Oct. 28 Reapp. Nov. 13 Reapp. Nov. 29 Disapp. Nov. 29 Reapp. Dec. 15 Disapp. Dec. 15 Reapp. Dec. 31 Disapp. Dec. 31 Reapp. 1908. Jan. 16 Disapp. Jan. 16 Reapp. SHADOW OF TITAN AND DISK OF TITAN. Crossing the minor axis of the planet at the distance y from the center. Gr. M. T. J r P lh23m 15' '.8 104** West. 7 0 I .4 128 0 27 17 .1 105 6 14 2 .0 130 23 33 17 .0 106 5 26 1 •5 134 22 40 15 .5 106 4 37 0 .0 141 21 49 12 .5 105 21 0 8 .0 104 20 13 2 .6 lOI I 9 2 .2 91 East 0 15 6 .9 85 23 19 10 .6 82 22 22 13 .0 81 16 56 0 .9 71 21 22 13 .8 82 16 27 I .9 77 20 19 13 .0 83 16 3 2 .0 84 19 9 ID .8 87 15 51 I .9 93 17 48 7 .3 92 Gr. M. T. y Semi-duration of transit. 1907. June 15 Shadow ph 56m i".9 South 3^.0 June 15 Disk 16 2 6.4 North I .7 July I Shadow 9 5 I .2 South 3 .0 July I Disk 15 7 7 .0 North I .5 July 17 Shadow 8 16 0 .5 South 3 .0 July 17 Disk 13 48 7 .0 North I .6 Aug. 2 Shadow 7 30 0 .2 North 3 0 Aug. 2 Disk 12 6 6.3 North 2 .0 Aug. 18 Shadow 6 43 0 .9 North 3 .0 Aug. 18 Disk 9 51 5 .0 North 2 .5 128 Publications of the 1907. 1908. Gr. M. T. y Semi-duration of transit. Sept. 3 Shadow s"- 59" r.6 North 3^0 Sept. 3 Disk 7 42 3 .2 North 2 .8 Sept. 19 Disk * 0 14 I .3 North 3 .0 Sept. 19 Shadow 5 15 2 .3 North 2 .9 Oct. 5 Disk 2 48 0 .7 South 3 .0 Oct. 5 Shadow 4 33 2 .9 North 2 .9 Oct. 21 Disk 0 31 2 .2 South 2 .9 Oct. 21 Shadow 3 49 3.6 North 2 .8 Nov. 5 Disk 22 32 3 I South 2 .8 Nov. 6 Shadow 3 5 4 .3 North 2 .6 Nov. 21 Disk 20 46 3 .4 South 2 .8 Nov. 22 Shadow 2 21 4 .9 North 2 .4 Dec. 7 Disk 19 47 2 .9 South 2 .8 Dec. 8 Shadow I 34 5 .5 North 2 .1 Dec. 23 Disk 19 2 I .8 South 2 .9 Dec. 24 Shadow 0 48 6 .2 North I .8 Jan. 8 Disk 18 42 0 .2 South 3 .0 Jan. 8 Shadow 23 59 6 .8 North I .2 Jan. 24 Disk 18 42 I .7 North 3 .0 Jan. 24 Shadow? 23 6 7 .4 North • ECLIPSES OF THE INNER SATELLITES OF SATURX, 1907. DIS.XPPEARANCE BEFORE OPPOSITION. s ami /» denote the geocentric place of the satellite at the time of its disapf)t'ar- ancc. i. e. the int of the minor axis to the west. Gr. M. T. / /» Gr. M. T. / /» : 20 Mi oh 42m 2".3 9i°West June 28 Te 9*^44™ 3''-9 94° \> Rh 4 2 7 .2 100 1 Mi 12 16 MM mmm 91 Di 4 5 5 .2 99 1 En 13 55 3 .2 96 En 8 36 3 .2 96 29 Rh 4 55 7 .4 I IX) Te 20 29 3 .9 94 1 Mi 10 53 2 .2 91 Mi 23 19 2 .3 91 En 22 48 3 .2 96 21 En 17 29 3 .2 9(3 30 Te 7 2 3 .8 94 Mi 21 ^6 2 .3 91 Mi 9 30 2 .2 91 22 Te 17 48 3 .9 94 July 1 Di 2 51 5 .2 99 Mi 20 33 2 .3 91 En 7 41 3 I 96 Di 21 46 5 .2 99 1 Mi 8 7 2 .2 91 23 TiD 0 27 17 I 105 1 2 Te 4 21 3 .8 94 En 2 22 3 .2 96 Mi 6 44 2 .2 91 TiR 6 14 2 .0 130 En 16 34 3 I 96 Mi iQ 10 2 .3 91 3 Mi 5 21 2 .2 91 24 En II 15 3 .2 96 Rh 17 22 7 .4 lOI Te 15 7 3 -9 94 Di 20 33 5 .2 99 Rh 16 28 7 -3 100 4 En I 27 3 I 96 Mi 17 47 2 .3 91 Te I 39 3 .8 94 25 Di 15 28 5 .2 99 Mi 3 58 2 .2. 91 Mi 16 25 2 .3 91 5 Mi 2 36 « 2 .2 92 En 20 9 3 .2 96 1 En 10 21 3 I 96 26 Te 12 25 3 .9 94 1 Te 22 58 3 .8 94 Mi 15 2 2 .3 91 6 Mi I 13 2 .2 92 27 En 5 2 3 .2 96 Di 14 15 5 .1 99 Mi 13 39 2 .3 91 En 19 14 3 I 96 28 Di 9 10 5 -2 99 Mi 23 50 2 .2 92 Astronomical Society of the Pacific. 129 fr 7 8 10 II 12 13 15 16 17 18 19 20 21 22 23 24 25 26 Te Mi En Rh Mi Gr. M. T. 22 27 4 7 5 49 21 4 Ti D 23 33 TiR 5 26 Di En Tc Mi Mi En Te Mi Di En Mi Rh Tc Mi En Mi Di En Tc Mi En Mi Rh Te Mi Di En Mi En Te Mi Mi Di En Te Mi Rh En Mi Te Mi Oi En Mi En Te Mi 7 13 56 0 17 35 19 41 18 18 21 53 14 54 16 55 I 6 38 47 15 33 18 16 12 12 14 10 15 40 12 47 19 20 o 33 9 31 II 24 9 10 6 6 26 I 43 50 8 38 13 I 18 19 7 15 3 4 5 4 6 12 I 3 12 8 52 30 43 6 27 7 19 10 20 59 I 44 22 45 o 21 o 25 5 52 22 58 14 45 20 4 21 35 TiD 22 40 TiR 4 37 Di 18 7 Mi En Rh Tc 20 12 23 38 7 37 17 23 s 3''.8 2 .2 3 I 7 .3 2 .2 17 I .0 .5 5 I 3 I 3.8 2 .2 2 .2 3 .0 3 .7 2 .2 5 I 3 -o 2 .2 7 -2 3 .7 2 .2 3 .0 2 .2 5 .0 3 .0 3 .7 2 .1 3 .0 2 .1 7 .0 3 .7 2 .1 5 .0 3 .0 2 .1 2 .9 3.6 2 .1 2 .1 4 .9 2 .9 3.6 2 .1 6.7 2 .9 2 .0 3 .5 2 .0 4.8 2 .8 2 .0 2 .8 3 4 2 .0 15 -5 O .0 4 .7 2 .0 2 .8 64 3 .3 P 94''West 92 96 lOI 92 106 134 99 96 94 92 92 96 94 92 99 96 92 lOI 94 92 96 92 99 96 94 92 96 92 lOI 94 92 99 96 92 96 94 92 92 99 96 94 92 100 96 92 94 92 99 96 92 96 94 92 106 141 99 92 96 100 94 July 26 Mi 27 En Mi 28 Di Te Mi En 29 Mi 30 En Te Mi Rh 31 Di En Mi Aug. I Te Mi En 2 Mi Di 3 En Tc Mi 4 Mi Rh En 5 Te Mi Di En 6 Mi 7 Te Mi En 8 Mi Di En Rh Te Mi 9 Ti Mi 10 En Te Mi 11 Di En Mi 12 Te Mi En 13 Rh Mi Di 14 En Te Mi 15 En Mi 16 Te Mi Gr. M. T. l8h 50m 8 31 17 27 11 48 14 41 16 4 17 25 14 41 2 18 12 o 13 18 20 5 II 4 30 II II 55 9 19 10 33 20 4 9 10 2Z 12 5 6 7 6 57 37 47 24 8 32 13 51 3 56 5 I 16 54 22 44 3 39 1 15 2 16 7 37 0 53 10 36 16 30 20 59 22 33 23 30 21 49 22 7 1 24 19 52 20 45 4 17 .10 17 19 22 17 II 17 59 19 10 9 26 16 36 21 59 4 3 14 29 15 13 12 56 13 51 11 48 12 28 1 .9 2 .7 I .9 4 .6 3 .3 1 .9 2 .7 1 .9 2 .7 3 2 1 .8 6 .2 4 -5 2 .6 I .8 3 I 1 .8 2 .6 I .8 4 2 3 ■3 •5 .0 I .8 I .7 5 2 2 I .8 .5 .9 .7 4 .1 2 .4 1 .7 2 .8 1 .7 2 .3 1 .7 3 -9 2 .3 5 .4 2 .8 I .6 12 .5 1 .6 2 .2 2 .7 1 .6 3 .7 2 .2 1 .5 2 .6 1 .5 2 .2 4 .9 1 -5 3 .5 2 .1 2 .5 1 .5 2 .0 1 .4 2 .3 I .4 P 92® West 96 92 99 94 92 96 92 96 94 92 100 99 96 92 94 92 96 92 99 ' 96 94 92 . 92 'lOO 96 94 92 98 96 92 94 92 96 92 98 96 100 93 92 105 92 96 93 92 98 95 92 93 92 95 99 92 98 95 93 92 95 92 93 92 130 Publications of the Gr. M. T. J r P Gr. M. T. s P Aug. 1 6 Di I5h4ira 3".3 98*'West Sept. 2 Te lit 137m i''.3 91** We En 21 50 I •9 95 Mi II 38 0 •7 92 17 Mi II 5 I •4 92 3 Mi 10 15 0 •7 92 Rh 21 53 4 .5 99 En 17 22 0 .9 94 18 En 6 43 I .8 95 4 Mi 8 53 0 .6 92 Te 9 7 2 .2 93 Te 8 55 I .1 90 Mi 9 42 I .3 92 Di 19 35 I .5 96 19 Mi 8 19 I .3 92 Rh 23 43 2 •7 97 Di 9 23 3 .0 98 5 En 2 15 0 & 94 En 15 36 I .8 95 Mi 7 30 0 .6 92 20 Te 6 25 2 .1 92 6 Mi 6 7 0 M 0 92 Mi 6 57 I •3 92 Te 6 14 I .0 90 21 En 0 29 I .7 95 En II 9 0 .7 94 Mi 5 34 I •3 92 7 Mi 4 44 0 •5 92 22 Di 3 5 2 .8 97 Di 13 17 I .2 95 Te 3 44 2 .0 92 En 20 2 0 •7 94 Mi 4 II I .2 92 8 Mi 3 22 0 .5 92 En 9 23 I .7 95 Te 3 ^^ 0 .8 90 Rh 10 21 3 .9 99 9 Mi I 59 0 .4 92 23 Mi 2 48 I .2 92 En 4 55 0 .6 93 En 18 16 I .6 95 Rh 12 II I .6 96 24 Te I 3 I .9 92 10 Mi 0 36 0 .4 92 Mi I 26 I .2 92 Te 0 52 0 •7 90 Di 20 47 2 •5 97 Di 6 59 0 .9 95 25 Mi 0 3 I .1 92 En 13 49 0 .5 93 En 3 9 I .5 95 Ti 20 13 2 .6 lOI Ti 21 0 8 .0 104 Mi 23 14 0 .3 92 Te 22 22 I .8 91 II Mi 21 51 0 .3 92 Mi 22 40 I .1 92 Te 22 .11 0 .5 89 26 En 12 2 I .4 95 En 22 42 0 .4 93 Mi 21 17 I .1 92 12 Mi 20 28 0 .2 92 Rh 22 48 3 .4 98 13 Di 0 41 0 .6 94 27 Di 14 29 2 .3 97 En 7 35 0 .3 93 Te 19 40 I .6 91 Mi 19 5 0 .2 92 Mi 19 55 I .0 92 Te 19 30 0 •3 89 En 20 56 I .3 95 14 Rh 0 39 0 .7 95 28 Mi 18 32 0 .9 92 En 16 29 0 .2 92 29 En 5 49 I .2 94 Mi 17 43 0 .1 92 Te 16 59 1 .5 91 15 Mi 16 20 0 .1 92 Mi 17 9 0 .9 92 Te 16 48 0 .2 89 30 Di 8 II 2 .0 96 Di 18 23 0 .3 ■ 94 En 14 42 I .2 94 16 En I 22 0 .1 92 Mi 15 46 0 .8 92 Mi 14 57 0 .0 92 31 Rh II 16 2 .7 98 17 En 10 15 0 .1 92 Te 14 18 I .4 91 Mi 13 35 0 .0 92 Mi 14 24 0 .8 92 Te 14 7 0 .1 89 En 23 35 I .1 94 18 Di 12 5 0 .1 93 Sept. I Mi 13 I 0 .7 92 Mi 12 12 0 .0 92 2 Di I 53 I .8 96 Rh 13 6 0 .1 94 En 8 29 I .0 94 En 19 9 0 .0 92 REAPPEARANCE AFTER OPPOSITION. s and p denote the geocentric place of the satellite at the time of its reappear- ance, i. e. the distance from the limb of the f>lanet, and the position-angle, counted from the north point of the minor axis to the east. Gr. M. T. / p Gr. M. T. s p Sept. 17 Mi I5*»55"^ o".o 95" East Sept. 18 En 21 h 49m 0^.0 92** Ea Te 17 6 0 .0 90 19 Mi 13 9 0 .0 95 18 Mi 14 Z2 0 .0 95 Te 14 25 0 .0 90 Di 15 25 0 .0 93 20 En 6 43 0 .1 92 Rh 17 3 0 .0 93 Mi II 47 0 .1 95 Astronomical Society of the Pacific. 131 Gr. M. T. J P ept. 21 Di 9I I 701 0.''2 92** East Mi 10 24 0 .1 95 Te II 44 0 .1 90 En 15 36 0 .2 92 22 Mi 9 I 0 .2 95 23 En 0 29 0 .3 91 Rh 5 31 0 .6 92 Mi 7 39 0 .2 95 Te 9 3 0 .3 89 24 Di 2 50 0 .4 92 Mi 6 16 0 .2 94 En 9 23 0 .4 91 25 Mi 4 53 0 .3 94 Te 6 21 0 .5 89 En 18 16 0 .4 91 26 Mi 3 30 0 .3 94 Di 20 32 0 .6 91 27 Ti I 9 2 .2 91 Mi 2 8 0 .4 94 En 3 9 0 .5 91 Te 3 40 0 .6 89 Rh 17 58 I .2 91 28 Mi 0 45 0 .4 94 En 12 3 0 .6 91 Mi 23 22 0 .4 94 29 Te 0 59 0 .8 89 Di 14 14 0 .9 91 En 20 56 0 .7 91 Mi 22 0 0 .4 94 30 Mi 20 37 0 .5 94 Te 22 18 0 .8 89 kt. I En 5 50 0 .8 91 Mi 19 14 0 .5 94 2 Rh 6 26 I .8 90 Di 7 56 I .2 90 En 14 43 0 .8 91 Mi 17 52 0 .6 94 Te 19 37 I .0 88 3 Mi 16 29 0 .6 94 En 23 36 0 .9 90 4 Mi 15 6 0 .6 94 Te 16 56 I .1 88 5 Di I 38 I -4 90 En 8 30 0 .9 90 Mi 13 43 0 .7 94 6 Mi 12 21 0 .7 94 Te 14 15 I .3 88 En 17 23 I .0 90 Rh 18 53 2 .3 89 7 Mi 10 58 0 .8 94 Di 19 20 I .6 89 8 En 2 16 I .1 90 Mi 9 35 0 .8 94 Te n 34 I .4 88 9 Mi 8 13 0 .8 94 En II 10 I .1 90 10 Mi 6 50 0 .9 94 Te 8 53 I .5 88 Di 13 2 I .9 89 En 20 3 I .2 90 II Mi 5 27 0 .9 93 Oct. II Rh 12 Mi En Te 13 Ti Mi Di En 14 Mi Te En Mi 15 Rh Mi i6 Di Te En Mi 17 En Mi Te 18 Di Mi 19 En Mi Te 20 Rh En Mi 21 Di Mi Te En 22 Mi 23 En Mi Te 24 Di Mi En Rh 25 Mi Te En 26 Mi Di 27 Mi En Te 28 Mi En Ti 29 Mi Te Rh Di 30 En Mi 31 Mi Te En Gr. M. T. s P yh. 2im 2".9 SS^'East 4 5 0 .9 93 4 57 I .3 90 6 12 I .7 88 0 15 6.9 85 2 42 I .0 93 6 44 2 .2 88 13 50 I .3 89 I 19 I .0 93 3 31 I .8 87 22 43 I .4 89 23 56 I .0 93 19 49 3 .4 88 22 34 I .0 93 0 26 2 .4 88 0 50 2 .0 87 7 37 I .5 89 21 II I .0 93 16 30 I .6 89 19 48 I .1 93 22 9 2 .0 87 18 8 2 .6 88 18 26 I .1 93 I 24 I .6 89 17 3 I .1 93 19 28 2 .2 87 8 16 3 .9 87 10 17 I .7 89 15 40 I .2 93 II 51 2 .8 88 14 18 I .2 93 16 47 2 .3 87 19 II I .7 89 12 55 I .2 93 4 4 I .8 88 II 32 I .3 93 14 6 2 .4 87 5 33 3 .0 87 10 10 I -3 93 12 57 I .8 88 20 44 4 .4 86 8 47 I .3 93 II 25 2 .5 87 21 51 I .9 88 7 24 I .3 93 23 15 3 .2 87 6 2 I .4 93 6 44 2 .0 88 8 44 2 .6 87 4 39 I .4 93 15 38 2 .0 88 23 19 10 .6 82 3 16 I .4 93 6 3 2 .7 87 9 12 4 .9 85 16 57 3 .4 87 0 31 2 .1 88 I 54 I -5 93 0 31 I .5 93 3 22 2 .8 87 9 25 2 .1 88 132 Publications of the Gr. M. T. < r P Gr. M. T. J r P Oct. 31 Mi 23h 8m r '.5 93® East Nov. 20 Rh 23h 31™ 6" .2 85*" East Nov. I Di 10 39 3 .5 87 21 Mi 16 50 I .9 92 En 18 18 2 .2 88 22 En 7 41 2 .8 88 Mi 21 46 I .5 93 Mi 15 27 2 .0 92 2 Te 0 41 2 .8 86 Te 19 10 3 •4 86 Mi 20 2Z I .6 93 23 Di 8 18 4 .4 86 Rh 21 40 5 .2 85 Mi 14 4 2 .0 92 3 En 3 12 2 .2 88 En 16 34 2 .8 88 Mi 19 0 I .6 92 24 Mi 12 42 2 .0 92 Te 22 0 2 .9 86 Te 16 29 3 .5 86 4 Di 4 22 3 .7 87 25 En I 28 2 .8 88 En 12 ^ 5 2 •3 88 Mi II 19 2 .0 92 Mi 17 38 I .6 92 Rh II 59 6 .3 85 5 Mi 16 15 I .6 92 26 Di 2 0 4 .5 86 Te 19 19 3 .0 86 Mi 9 56 2 .0 92 En 20 59 2 .3 88 En 10 21 2 .8 88 6 Mi M 52 I .7 92 Te 13 48 3 0 86 Di 22 4 3 .8 87 27 Mi 8 34 2 .0 92 7 En 52 2 .4 88 En 19 15 2 .8 88 Rh 10 7 5 .5 .85 28 Mi 7 II 2 .0 92 Mi 13 30 I .7 92 Te II 7 3 .5 86 Te 16 38 3 .1 86 Di 19 42 4 .5 86 8 Mi 12 7 I 92 29 En 4 8 2 .8 88 En 14 46 2 .4 ^ Mi 48 2 .0 92 9 Mi 10 44 I .7 92 TiD 16 56 0 .9 71 Te 13 57 3 .2 86 TiR 21 22 13 .8 82 Di 15 46 4 .0 87 30 Rh 0 27 6 •4 85 En 23 39 2 .5 88 Mi 4 25 2 .0 92 10 Mi 9 22 I .8 92 Te 8 26 3 .5 86 II Mi 7 59 I .8 92 En 13 2 2 .8 88 En 8 ZZ 2 .5 88 Dec. I Mi 3 3 2 .0 92 Te II 16 3 .2 86 Di 13 25 4 •5 86 Rh 22 35 5 .7 85 En 21 55 2 .8 ^ 12 Mi 6 36 I .8 92 2 Mi I 40 2 .1 92 Di 9 29 4 .1 86 Te 5 46 3 .6 87 En 17 26 2 ^ 3 Mi 0 17 2 .1 92 13 Mi 5 14 I .8 92 En 6 49 2 .9 88 Te 8 35 3 .3 86 Mi 22 55 2 .1 92 ' Ti 22 22 13 .0 81 4 Te 3 5 3 .6 87 14 En 2 20 2 .6 88 Di 7 7 4 m 0 96 Mi 3 51 I .8 92 Rh 12 54 6 .5 86 15 Mi 2 28 I .9 92 En 15 42 2 .9 88 Di 3 II 4 .2 86 Mi 21 32 2 .1 92 Te 5 54 3 .3 86 5 Mi 20 9 2 .1 92 En II 13 2 .6 88 6 Te 0 24 3 .6 87 16 Mi I 6 I .9 Q2 En 0 36 2 .9 88 Rh II 3 6 .0 85 Mi 18 47 2 .1 92 En 20 7 2 .7 88 7 Di 0 49 4 .5 87 Mi 23 43 I .9 02 En 9 29 2 .9 88 17 Te 3 13 3 .4 86 Mi 17 24 2 .1 92 Di 20 53 4 .3 86 Te 21 43 3 .6 87 Mi 22 20 I .9 92 8 Mi 16 I 2 .1 92 18 En ^ D 0 2 .7 87 En 18 23 2 .9 88 Mi 20 58 I .9 92 9 Rh I 22 6 .5 86 19 Te 0 32 3 .4 86 Mi 14 38 2 .1 92 En 13 54 2 •7 88 Di 18 32 4 •5 87 Mi 19 35 I .9 92 Te 19 2 3 .6 87 20 Di 14 35 4 .4 86 10 En 3 16 2 .9 88 Mi 18 12 I .9 92 Mi 13 16 2 .1 92 Te 21 51 3 .4 86 II Mi II 53 2 .1 92 En 22 47 2 .7 88 En 12 10 2 .9 88 Astronomical Society of the Pacific. 133 Gr. M. T. f P Gr. M. T. * f P 11 Te l6h 2im 3'' '.6 87*" East Dec. 31 Mi 6h 56111 2' '.0 92''East 12 Mi 10 30 2 .1 92 Rh 15 41 5 .9 88 Di 12 14 4 .5 87 TiD 16 3 2 .0 84 En 21 3 2 .9 88 Di 16 10 4 .2 89 13 Mi 9 8 2 .1 92 TiR 19 9 10 .8 87 Te 13 40 3 .6 88 1908 Rh 13 50 6 .4 87 Jan. I En I 32 2 .6 89 14 En 5 57 2 .9 88 Mi 5 33 I •9 92 Mi 7 45 2 .1 92 Tc 10 51 3 •3 89 15 Di 5 56 4 ■5 88 2 Mi 4 10 I .9 92 Mi 6 22 2 .1 92 En 10 25 2 .6 90 Te 10 59 3 .6 88 3 Mi 2 47 I .9 92 En 14 50 2 .9 88 Te 8 10 3 •3 90 TiD 16 27 I •9 77 Di 9 52 4 .1 90 TiR 20 19 13 .0 83 En 19 19 2 .6 90 16 Mi 4 59 2 .1 92 4 Mi I 25 I •9 92 En 23 44 2 .9 88 5 Mi 0 2 I .9 92 17 Mi 3 37 2 .1 92 Rh 4 9 5 .7 89 Te 8 18 3 .6 88 En 4 12 2 .5 90 Di 23 39 4 •5 88 Te 5 29 3 .2 90 18 Mi 2 14 2 .1 92 Mi 22 39 I •9 92 Rh 2 18 6 .4 87 6 Di 3 34 4 .0 90 En 8 Z7 2 •9 88 En 13 6 2 •5 90 19 Mi 0 51 2 .1 92 Mi 21 16 I .9 92 Te 5 37 3 .6 88 7 Te 2 48 3 .2 90 En 17 31 2 .9 89 Mi 19 43 I .9 92 Mi 23 28 2 .1 92 En 21 59 2 .5 90 20 Di 17 21 4 .4 88 8 Mi 18 31 I .9 92 Mi 22 6 2 .1 92 Di 21 17 3 .9 90 21 En 2 24 2 .8 89 9 Te 0 7 3 .1 90 Te 2 56 3 .5 88 En 6 53 2 .4 90 Mi 20 43 2 .1 92 Rh 16 37 5 .5 90 22 En II 18 2 .8 89 Mi 17 8 I .9 92 Rh 14 46 6 .3 87 10 Mi 15 45 I .9 92 Mi 19 20 2 .0 92 En 15 46 2 .4 91 23 Te 0 15 3 .5 89 Te 21 26 3 .0 91 Di II 3 4 •4 89 II Mi 14 22 I .9 92 Mi 17 38 2 .0 92 Di 14 59 3 .8 91 En 20 II 2 .8 89 12 En 0 40 2 .3 91 24 Mi 16 35 2 .0 92 Mi 13 0 I .8 92 Te 21 34 3 .5 89 Te 18 45 3 .0 91 25 En 5 5 2 .8 89 13 En 9 33 2 .3 91 Mi 15 12 2 .0 92 Mi II 37 I .8 92 26 Di 4 45 4 .3 89 14 Rh 5 5 5 .1 91 Mi 13 49 2 .0 92 Di 8 41 3 .6 92 En 13 58 2 .8 89 Mi 10 14 I .8 92 Te 18 53 3 .4 89 Te 16 4 2 .9 91 27 Rh 3 13 6 .1 88 En 18 27 2 •3 91 Mi 12 27 2 .0 92 15 Mi 8 51 I .8 92 En 22 52 2 .7 89 16 En 3 20 2 .2 91 28 Mi 11 4 2 .0 92 Mi 7 28 I .8 92 Te 16 12 3 .4 89 Te 13 23 2 .8 91 Di 22 28 4 .3 89 TiD 15 51 I .9 93 29 En 7 45 2 .7 89 TiR 17 48 7 .3 92 Mi 9 41 2 .0 92 17 Di 2 23 3 .4 92 30 Mi 8 18 2 .0 92 Mi 6 6 I .8 92 Te 13 31 3 .3 89 ' En 12 14 2 .2 91 En 16 39 2 .7 89 18 Rh 17 33 4 .8 91 134 Publications of the SHADOWS OF THE SATELLITES OF TETHYS, DIOXE, RHEA. Crossing the minor axis of the disk at the distance y from the center. June 21 Di Te 22 Rh 23 Te 24 Di 25 Te 27 Rh Di Te 29 Te Di July I Te Rh 2 Di 3 Te 5 Te Di 6 Rh Te 8 Di Te 10 Rh Te Di 12 Te 13 Di 14 Te 15 Rh 16 Di Te 18 Te Di 19 Rh 20 Te 21 Di 22 Te 23 Te 24 Rh Di 25 Te 27 Di Te 28 Rh 29 Te Di 31 Te Aug. I Di 2 Rh Te 4 Te Di 6 Te Rh 7 Di 8 Te 9 Di Te // Rh Gr. M. T. I4K7 20 .8 12 .4 18 .1 8 .4 0 .8 2 .1 12 .7 10 .0 19 .8 7 .3 13 .3 13 -5 4 .6 7 .-2 1 .7 23 .2 0 .9 20 .5 14 .2 17 .8 18 .6 12 .3 12 .5 2 .6 6 .0 9 .8 7 .1 23 .7 15 .0 4 .4 17 .4 1 .7 23 .0 3 .5 11 .0 20 .3 4 7 17 .6 15 .9 14 .9 22 .4 12 .2 16 .1 4 -4 9 .6 6 .9 9 .8 4 .2 16 .8 3 .5 I .5 21 .2 22 .8 5 .3 0^.3 South o .8 o .5 o .8 0 .2 o .7 o .4 o .2 o .7 o .7 O .1 o .7 o .3 O .1 o\6 o .6 o .0 o .2 o .6 o .0 o .6 o .2 o .5 0 .1 North o .5 South 0 .1 North 0 .5 South o .1 0 .2 North o .5 South 0 .4 o .2 North o .0 o .4 South o .3 North o .4 South 0 .4 o .1 North o .3 o .3 South o .4 North o .3 South o .1 North o .3 South o .4 North o .3 South o .5 North o .2 o .2 South o .2 o o North o .2 South o .3 North o .5 o .2 South o .6 North o .1 South o .4 North \ Aug. 1 1 12 13 15 17 18 19 20 21 23 24 25 26 28 29 30 31 Sept. I 2 3 5 6 7 8 9 II 12 M 16 17 18 19 20 22 24 25 26 28 29 Te Di Te Di Te Rh Te Di Te Rh Di Te Te Di Rh Te Di Te Te Di Rh Te Di Te Rh Te Di Te Di Te Rh Di Te Te Di Rh Te Di Te Rh Te Di Te Di Te Rh Te Di Te Rh Di Te Te Di Te Rh Gr. M. T. 20^.1 14 .9 17 .4 8 .6 14 .7 17 .7 12 .0 2 .3 9 .3 6 .2 20 .0 6 .6 3 -9 13 .6 18 .6 I .2 7 .3 22 .6 19 .9 I .0 7 .0 17 .2 18 .7 14 .5 19 .5 11 .8 12 .4 9 I 6 .1 6 .4 7 .9 23 .8 3 7 I .0 17 .5 20 .4 22 .3 II .2 19 .6 8 .8 17 .0 4 .9 14 .3 22 .6 II .6 21 .2 8 .9 16 .2 6 .2 9 .7 9 .9 3 .5 o .8 3.6 22 .1 22 .2 2\ .^ O .1 o. .6 O .1 o .6 o .1 o .4 o .0 o .7 O .0 o .5 o .7 O .0 O .0 o .7 o .6 O .1 o .8 o .1 o .1 o .8 o .6 o .1 0 .9 o .2 South North South North South North o o .7 .2 o .9 O .2 0 .9 O .2 O I .8 .0 o .3 o .3 I o .0 .8 0 .3 1 .1 o .3 o .9 0 .4 1 .1 0 .4 1 .1 o .4 o .9 o .4 I .2 0 .5 I .0 I .2 o .5 o .5 I .2 0 .5 1 .1 I .3 Astronomical Society of the Pacific. 135 Gr. M. T. y Gr. M. T. y Oct. I Te 19^.4 0^.5 North Nov. 25 Te I3**.6 i^ '.3 North 3 Di 15 0 I -3 27 Di 9 .0 I .9 Te 16 .8 0 .6 Te 10 .9 I •3 4 Rh 10 .6 I .1 Rh 16 .1 2 .0 5 Te 14 .1 0 .6 29 Te 8 .2 I .3 6 Di 8.7 I .3 30 Di 2 .8 2 .0 7 Te II 4 0 .6 Dec. I Te 5 .5 I 4 8 Rh 23 .0 I .2 2 Rh 4.6 2 .1 9 Di 2 4 I .3 Di 20 .4 2 .0 Te 8.7 0 .6 3 Te 2 .8 I 4 II Te 6 .0 0 .6 5 Te 0 .1 I .4 Di 20 .1 I .4 Di 14 .2 2 .1 13 Te 3 .3 0 .7 6 Rh 17 .0 2 .1 Rh II .5 I .3 Te 21 .5 I .5 14 Di 13 .8 I -4 8 Di 7 .9 2 .1 15 Te 0 .6 0 .7 Te 19 .8 I •5 16 Te 21 .9 0 7 10 Te 16 .1 I .5 17 Di 7 .5 I 4 II Di I .6 2 .1 18 Rh 0 .0 I -3 Rh 5 .5 2 .2 Te 19 .2 0 .7 12 Te 13 .4 I •5 20 Di I .2 I -4 13 Di 19 .3 2 .2 Te 16 .6 0 .7 14 Te 10 .7 I .6 22 Rh 12 4 I .4 15 Rh 18 .0 2 .3 Te 13 -9 0 .8 16 Te 8 .0 I .6 Di 18 .9 I .5 Di 13 .0 2 .2 24 Te II .2 0 .8 18 Te 5 .4 I .6 25 Di 12 .6 I .5 19 Di 6 .7 2 .3 26 Te 8 .5 0 .8 20 Te 2 .7 I .6 27 Rh 0 .9 I 5 Rh 6.5 2 .4 28 Te 5 .8 0 .8 22 Te 0 .0 I .7 Di 6.3 I .5 Di 0 .4 2 .3 30 Te 3 I 0 .9 23 Te 21 .3 I .7 31 Di 0 .0 I .6 24 Di 18 .1 2 •3 Rh 13 .3 I .5 Rh 18 .9 2 .5 Nov. I Te 0 .5 0 .9 25 Te 18 .6 I .7 2 Di 17 .7 I .6 27 Di n .8 2 .4 Te 21 .8 0 .9 Te 16 .0 I .8 4 Te 19 .1 0 .9 29 Rh 7 .4 2 .5 5 Rh I .8 I .6 Te 13 .3 I .8 Di II 4 I .6 30 Di 5 -5 2 .4 6 Te 16 4 I .0 31 Te 10 .6 I .8 8 Di 5 I I .7 1908. Te 13 .7 I .0 Jan. I Di 23 .2 2 .5 9 Rh 14 .3 I .7 2 Te 7 .9 I .9 10 Te II .0 I .0 Rh 19 .9 2 .6 Di 22 .8 I .7 4 Te 5 .2 I .9 12 Te 8.3 I .0 Di 17 .0 2 .5 13 Di 16 .5 I .7 6 Tc 2 .6 I •9 14 Rh 2 .7 I .8 7 Rh 8.3 2 .7 Te 5 .6 I .1 Di 10 .7 2 .6 16 Te 3 .0 I .1 Tc 23 -9 2 .0 Di 10 .2 I .8 9 Te 21 .2 2 .0 18 Te 0 .3 I .1 10 Di 4 .4 2 .6 Rh 15 .2 I .8 II Te 18 .5 2 .0 19 Di 3 .9 I .8 Rh 20 .8 2 .7 Te 21 .6 I .2 12 Di 22 .1 2 .7 21 Te 18 .9 I .2 13 Te 15 .8 2 .1 Di 21 .6 I .8 15 Te 13 .2 2 .1 23 Rh 3 .6 I .9 Di IS .8 2 .7 Te 16 .2 I .2 i 16 Rh 9 .3 2 ."B. 24 Di 15 '3 ^•P . 17 Te 10 -S 2 .1 136 Publications of the PLANETARY PHENOMENA FOR JULY AND AUGUST, 1907. By Malcolm McNeill. Last Quarter. . New Moon . . . First Quarter.. Full Moon . . . Last Quarter. . PHASES OF THE MOON, PACIFIC TIME. July 2, 6h 34ni A.M. New Moon Aug. 8, lo^ 36™ p.m. First Quarter.. ** 16, i 5 p.m. Full Moon " 23, 4 15 A.M. 24,8 30 P.M. Last Quarter.. " 30, 9 28 a.m. 31,6 25 p.m. 10,7 17 A.M. 18,5 12 A.M. The Earth reaches aphelion — that is, reaches its greatest distance from the Sun — July 5th, 7 a.m. Pacific time. There will be two eclipses during July. The first is an annular eclipse of the Sun on July loth, not visible in the United States. The path of central eclipse begins in the South Pacific, crosses South America, and ends in the South Atlantic. The second is a partial eclipse of the Moon on the evening of July 24th. The beginning of the actual eclipse is visible generally throughout North America except the northwest portion, and the end throughout North America except Alaska. The principal phases are as follows. Pacific time: — Moon enters penumbra, July 24, 5*^ 59™ p.m. Moon enters shadow.. 7 4 p.m. Middle of the eclipse.. 8 22 p.m. Moon leaves shadow... 9 41 p.m. Moon leaves penumbra 10 46 p.m. The maximum obscuration of the Moon is a little more than six tenths of the Moon's diameter. Mercury on July ist is an evening star, having passed great- est cast elongation on June 27th, and sets about an hour and one half after sunset. It is therefore at this time in fine posi- tion for observation, but it soon draws too near the Sun to be seen, and passes inferior conjunction on the evening of July 24th, becoming a morning star. It then moves rapidly away from the Sun, reaching greatest west elongation (18° 51') on August I2th. It then rises about an hour and one half before sunrise and will be an easy object in the morning twilight. By the end of the month it has nearly reached superior conjunction with the Sun. Astronomical Society of the Pacific. 137 Venus is still a morning star, rising i^ 24*" before sunrise July 1st, I** 3"^ August 1st, and less than half an hour before on August 30th. It cannot easily be seen by the naked eye much after the first week in August. By the end of that month it will nearly have reached superior conjunction with the Sun. During the latter part of July and through August Mercury, Venus, Jupiter, and Neptune are all very close together in the early morning sky just above the eastern horizon, and a good many conjunctions ocair. Mercury is in conjunction with Jupiter July 31st, 8 p.m., and with Venus at 5 a.m. on August 1st, — not very close approaches, Mercury being nearly 5° south in each case. Next, on August ist, 9 a.m., Venus and Jupiter are in conjunction, Venus being only 18' north of Jupiter. Mercury and Jupiter are again in conjunction on August loth. Mercury 2° 5' south. Mars comes to opposition with the Sun July 6th, 7 a.m. Pacific time, and is then above the horizon during the entire night. On August ist it is above the horizon until about 2 a.m., and on August 31st it sets about half an hour after midnight. During most of the period it is moving westward, having be- gi\n this motion on June 5th. From July ist to August 13th it moves about 8°, going back along a line somewhat south of its eastward motion in the spring, and at the latter date it occupies a position among the stars 5° south of its position on April i8th. From August 13th it moves eastward again, making about 4° before the end of the month, on a line a little north of the preceding westward motion. It does noi reach its minimum distance from the Earth until July 13th, a week after opposition, and throughout July its distance varies onlv a little more than two millions of miles. During: August the distance increases by about ten millions, and by the end of the month the brightness will diminish perceptibly, but will still exceed that of any of the fixed stars. Jupiter is still an evening star on July ist, but sets les- than an hour after sunset, and it will not be an easy object for naked-eye observation. It comes to conjunction with the Sun July 15th, II P.M., and becomes a morning star. On August 1st it rises about an hour before sunrise, and on August 31st nearly three hours before. Saturn rises at about 11^ 30*" p.m. on July 1st, at a\iOv\\. gh jQin pjif^ on August Tst and before 7^ 30"^ p.m. otv Xv\?^\s»\. 138 Publications of the Astronomical Society, &c. 31st. It moves about 7° westward and 1° southward in the constellation Pisces. On July ist the Earth is below and the Sun above the plane of the rings, so that we still have the dark face of the rings toward us. About July 2Sth the plane of the rings crosses the Sun, and from then until October Sun and Earth are on the same side of the plane. The rings are seen nearly edgewise, the minor axis being in the maximum at the end of July not more than four per cent of the major in the apparent ellipse, and this will diminish as the Earth approaches the plane of the rings. Uranus is in opposition to the Sun on July 3d, and is then above the horizon during the entire night. On August ist it sets at about 2^ 40™ a.m., and at about I2*» 40" a.m. on August 31st. During the two months it moves about 2° westward in the constellation Sagittarius north of the "milk-dipper." Uranus is not far from Mars throughout the two months, and is in conjunction with it twice,. — on July 19th, when Mars passes 5° 18' south of it, and again on August 24th, when Mars passes 4° 37' south, the motion of Mars being westward on the first occasion and eastward on the second. Neptune is in conjunction with the Sun on the morning of July 5th, and becomes a morning star. REVIEW. Resultate des Internationalen Breitendienstes. Vol. I (i903)» by Th. Albrecht. Vol. II (1906), by Th. Albrecht and B. Wanach. Centralbureau der Interna- tionalen Erdmessung; neue Folge der Veroffentlichungen, Nos. 8 und 13. In the latter part of 1899 six astronomical stations were established in the northern hemisphere for the purpose of making systematic observations for the latitude of each station in order to determine the variations in this quantity. Observa- tions at the six stations have been carried on continuously since they were established without serious interruption from any cause, and are to be continued into the future for an indefinite period of time. This work is being prosecuted by the Inter- national Geodetic Association, which has headquarters at Potsdam, Germany. This association was formed for the pur- pose of conducting geodetic undertakings which are inter- national in character. It is supported by the most prominent nations of the world, including nearly all the governments of Europe, the United States, the Argentine Republic, and Japan. The geodetic institutes of the various countries in which the latitude stations are located co-operate with the central station in carrying on this particular piece of work, the three stations in the United States being under the super- vision of the Coast and Geodetic Survey. Thus far the International Geodetic Association has pub- ished two volumes (under the title at the head of this review) giving the results of the observations for the variation of latitude. Volume I contains all of the observations made ^ The writer of this review has endeavored to make it both popular and tech- nical. It is hoped that the general reader may be able to get from it a general knowledge of the problems presented under the head of the variation of latitude and the methods by which they are attacked. It is hoped also that the profes- sional astronomer or the student of astronomy who cares to look into the subject more carefully may be able to get from it a fair idea of the details of the processes involved. No attempt has been made by the reviewer to explain in de- tail the parts which are purely technical and not essential to a general understand- ing of the problems involved. In a number of places the language of the authors has been followed quite closely, but in no case is the translation literal enough to warrant the use of quotation-marks. For some of the opinions expressed, and for Figure i, and for the computations under the theory of probabilities, the authors are in no wise responsible. In order to protect them, some of the state- ments, with which the reader might not agree, and for which the reveiwer alone is responsible, arc followed by the letter r in parenthesis. 140 Publications of the from the time the stations were established until January 4, 1902, and Volume II the observations obtained in the interval from January 5, 1902, to January 4, 1905. A third volume is in the course of preparation. The contents of Volume I are presented under eight head- ings, which are indicated by italics in the following paragraphs. Introduction. — The phenomenon of the variation of latitude was first detected in 1889 by Dr. Kustner, astronomer in the Royal Observatory at Berlin. Various observations and inves- tigations during the first half of the last decade of the nine- teenth century established the reality and the nature of the phenomenon, and steps toward a systematic and thorough attack upon the problems presented were first taken by the International Geodetic Association in 1895. In selecting the stations, social, hygienic, seismological, and meteorological, as well as mathematical, conditions were con- sidered, the prime requisite being, of course, that all of the stations should have a fair proportion of clear nights at all seasons of the year. Seventeen diflferent combinations of stations lying between latitudes -\- 36° 48' and -\- 44° 50', and including two combinations in the southern hemisphere on parallels — ^^° 54' and — 33° 27', were considered. The parallel of + 39° 8' was finally chosen with the stations located in Japan, in Italy, and in the eastern and western parts of North America. Two other stations were subsequently added, one in Central Asia and the other in the central part of North America, at Cincinnati. For the four stations first established — Mizusawa, Carloforte. Gaithcrsburg, and Ukiah — four new instruments exactly alike were constructed by Waxschaff in Berlin, loS"^"' aperture, 130^"^ focal length, 104 magnification. The instruments at Tschardjui and Cincinnati, by the same maker, are smaller, 68'"'" aperture, S/"^"^ focus, and 81'"'" aperture, ioo<^"» focus, respectively, both having 100 magnifying power. The Horrebow-Talcott method^ of observation was selected as the best suited for the purpose of determining the latitude. * Descriptions of this method may be found in any work on practical or general astronomy. The following statements concerning the method may be of help to those who are not familiar with its details. In order to make a determination of the latitude by this method it is necessary to measure, by means of an eye-piece micrometer attached to the zenith-telescope, the difference of zenith-distance of two stars of known declination which culminate at nearly equal zenith-distances. one north of and the other south of the zenith. The telescope is set at the mean Astronomical Society of the Pacific. 141 Twelve groups of stars, each containing six pairs at small zenith-distances I not more than 24°) and two pairs at large zenith-distance (about 60°), were selected. The stars were chosen by Dr. Kimura, astronomer in charge of the Japanese station at Alizusawa. The magnitudes of the stars lie between 4.0 and 7.4, and the intervals between their culminations vary between four and sixteen minutes. Two groups extending over four hours are observed each night according to the following programme : — I 0"- 21' Sept. 23 -Dec. 6 74 clays 35 Jays n 2-4 Nov. 2 -Jan. 4 64 III 4-6 Dec. 7 -Jan. 30 55 29 26 IV 6-8 Jan. 5 -Feb. 24 51 \^ 8-10 Jan. 31 -Mar. 2t 50 25 VI 10 -12 Feb. 25 -Apr. 15 50 25 VII 12 -14 Mar. 22- May 51 ■25 26 28 VIII 14 - 16 Apr. 16 - June 8 54 IX 16 -18 May 12 -July 9 50 X 18 -20 June 9 -Aug. U 66 3^ 35 XI 20-22 July 10- Sept. 22 75 XII 22-24 Aug. 14 -Nov. firit to So culminate » 40 40 af the leoiib aw the midd c of (he field of vie* Tbi. distance fr m the middle nf ihe lictd br ni»ns Df Ibe nic The in.tr iimenl is then •1 aiis. without disliirb i.g th setting, and the lele»coi« Ih u^ it did north of be l >»r w , abox or bclo. the and tbi« dia ance from the Miller it >e The propi . on Ihe two .tars g v« ih actual difle rence of their .ennh-dbun -Fi. whicb m provided th value of one nv<.lul>.>n D DbMTvaiiDii th« alao„ C«r-Kr™ be known. The 1 a. tiludj. if. 0 (he plats of * = m»^ + aj+y,(„^-m,)R + y,(i. + i,)+H ■-n-O. in «I>ich ilH lirsi lerm f the righl-hand mem r.prfMnts one rm one half Ihe difference of tb. e poinling of Ibe leldcape after diirrrif in Ihe atmospl Ibe Kcond. third, and fourth terms e the latiluite i> nothing other than Ihi eversal, detected by means of two very delitale nd the last term a small correction lot the iffccting the rays of light coming from J 142 Publications of the As two groups are observed each night, it is seen that each group will be observed both with the preceding and the follow- ing one, for lengths of time which vary between twenty-five and forty days. This interval is made to vary simply for the convenience of the observer, for by this means the observing time is made to come earlier in the evening during the winter months than during the summer months. In winter the obser- vations lie between. 7 p.m. and i a..m., in summer between 9 P.M. and 3 A.M. The time of beginning is never less than one and one-half hours after sunset, and the time of ending never less than one and three-quarter hours before sunrise. As the heating effects before sunrise are less pronounced than the cooling effects after sunset, it might perhaps have been w^ise to shift the whole programme a little further into the night, (r) The observatory buildings at the six stations are of similar construction but differ somewhat in details. The one at Ukiah 1 is three meters square, built of wood, with tin roof, and sur- rounded by an open slatwork construction which serves in some measure to protect the building within from the fierce ravs of the summer sun. The roof is divided in the meridian- line and mounted upon rollers so that the two halves may be rolled apart, one to the cast, the other to the west, giving a maximum opening of 1.8 meters. A small house to protect the meridian targets is located fifty-five meters north of the telescope. Description of the Stations. — Detailed descriptions of the six stations and their surroundings are given, covering eight pages of the quarto volume. A few of the chief facts only will be mentioned here. The city of Mizusawa (10,000 inhabitants) is situated on the principal Japanese island (Nippon), 466 kilometers north of Tokyo. The city lies in a north and south valley 180 kilometers long and five to fifteen kilometers wide. There are ranges of mountains to the east and to the west of the valley, the highest ])eak having an altitude of 2,200 meters. The valley is given larj:relv to tlic cultivation of rice. The observatorv is located about one kilometer south of the city. The number of earth- quakes at Mizusawa is large, but the locality is not affected by these disturbances as much as some other portions of Japan. The zenith-telescope at this station was injured during the transport from Potsdam and the observations obtained with it Astronomical Society of the Pacific, 143 during the first year were subject to rather large errors. There are two observers at Mizusawa, Dr. H. KimuRv\ and Dr. T. Nakano, who have served continuously since the observatory was estabHshed. Tschardjui is located east of the southern end of the Caspian Sea in the Central Asian possessions of the Russian Govern- ment. The station lies nine and one-half kilometers northwest of the city and three kilometers from the left bank of the Amu Daria or river Oxus. The observatory is located on an oasis in a sand-waste traversed by many canals. There is a greater range in the annual temperature at this station than at any of the others. The early observations at Tschardjui did not show a satisfactory agreement among themselves. This was found to be due to a poor level and the use of oil illumination. Electric illumination was substituted and the level discarded. It might not be out of place to remark, parenthetically, that it is now generally admitted that the heat from oil-lamps may have a very injurious effect upon observations in which a high degree of precision is expected. Since a satisfactory electric illumination for intermittent work may be obtained by the use of any good make of ordinary dry cells, there seems to be no longer any excuse for using oil illumination for work with a zenith-telescope or altazimuth, (r) Tschardjui is affected by very few earthquakes. The obser- vations at this station are made by a single observer. Several have thus far taken part, and they have all been officers of the Russian army. The Italian station has a very picturesque location on an old tower, San Vittorio, on the island of San Pietro, one kilometer southwest of the city of Carloforte. The tower is located on a peninsula on the east side of the island, so that the meridian of the observatory lies entirely over the Mediterranean Sea, with the exception of 260 meters to the north and 220 meters. to the south, and anomalies in the refraction would seem to be absolutely excluded. The island is free from mountains, the highest point being 211 meters above sea-level. The altitude of the observatory is twenty-two meters. Carloforte has 8,000 inhabitants and can be reached from Cagliari, the chief city of Sardinia, in eight hours. The island is free from earth- quakes, there having been only four in nearly four hundred years of any considerable intensity, and none of these destruc- Publications of the live. The observations at this station are made by two observers, who alternate with the nights. Several changes in the staff have taken place thns far, but all its members have been Italian astronomers. The Gaithersburg Observatory is located one kilometer south of the village of that name, which is thirty-three kilometers northwest of the city of Washington. The observatory has an altitude of 165 meters above sea-level ; tlie surrounding country is hilly. Mr. Edwin Smith, of the Coast and Geodetic Survey, made the observations at this station during the first year; Dr. Herman S. Davis during the succeeding five years. The work is now in charge of Dr. Frank E. Ross. After the parallel of 39° 8' had been selected for the location of the latitude stations it was found that this parallel passed through the grounds of the observatory of the University of Cincinnati, and Professor J. G. Porter, director of the observ- atory, volunteered to carry on observations if he were provided with an instrument. The observatory is located upon a hill, twenty meters higher than the surrounding country, eight kilometers northeast of the city, and two kilometers east of the Ohio River. The altitude of the observatory is 247 meters above sea-level. Thus far all of the observations, except a few during the summer months, have been made by Professor Porter. The California station is situated two kilometers south of the city of Ukiah, the county seat of Mendocino County. The observatory is located toward the western edge of one of the numerous small valleys in the Coast Range of mountains. The valley, which is traversed by the Russian River, is about fifteen kilometers long and from three to five kilometers wide, and surrounded by mountains of an average height of about 400 meters above the floor of the valley. The ahituile of the observatory is 220 meters above sea-level. Up to May, 1903, the observations at this station were made by Dr. Frank ScHLESiNGER, now director of the Allegheny Observatory; since that time the work has been in charge of the writer of this review. From a seismological point of view all of the American stations are favorably located. Although the Pacific Coast is well recognized as a region of seismic activity, yet the moun- tainous character of the country surrounding Ukiah seems to I Astronomical aociety of the Jfactfic. 145 afford a measure of protection from these disturbances. No earthquake since the observatory was establislied. not even the great shock of April 18, 1906, has been of sufficient intensity to in any way interfere with the progress of observations. Instrumental Constants. — The most important constants to be determined in the case of a zenith -telescope are the angular vaUie of one revolution of the micrometer-screw and the angular value of one space of the levels. The pairs of stars have been so chosen that an error in the value of a revolution of the micrometer-screw will be eliminated from the mean of the latitude derived from each group. If the mean of the decHnations of the stars of 3 pair, y> (&„ -j- S.), is less than the latitude it must be increased by half the difference of the zenith-distances as measured by means of the microm- eter. If '/i (K + S.) is greater than the latitude, then the micrometer correction is to be applied with a negative sign. If now the value of a revolution of the micrometer-screw used is too small, all of the micrometer corrections will be numer- icatly too small, and hence latitudes in the first case above will all be too small, and in the second case all too large. Hence, if in any group the sum of the positive micrometer corrections is made equal to the sum of the negative corrections, the errors will be eliminated in the mean latitude as determined from that group. On account of the precession this ehmination will hold only for a certain epoch, and the same group cannot therefore be used for an indefinite period. In the work of the International Geodetic Association the first selection of groups was used for six years, three years on either side of the epoch 1903.0. The angular value of one revolution of the micrometer- screws was detennined by the use of two methods, transits of polar stars at elongation, and measurement of differences of declination of stars as they come to the meridian. The second of these methods was used only at Cincinnati and Ukiah. The chief objection to it is that the results are affected by what- ever errors may pertain to the declinations of the stars used. The first method, transits of polar stars at elongation, is thco- reiically preferable, but in practice gives results which show rather a large and unsatisfactory range. This is very likely due to the fact that the observer must assume either that the angle between the line of sight of the telescope and the vertical J 146 Publications of the remains unchanged during the progress of the observations, an hour, more or less, or that any changes in this angle are truth- fully indicated by the readings of the latitude levels. Levels at their best are untrustworthy instruments, and in this case, since it is necessary for the observer to stand during the whole progress of the observations near the south end of the level tubes, it is easily conceivable that the heat from the observer's body may so affect the levels that a change in the reading of the bubbles may take place without any corresponding change in the pointing of the telescope, or vice versa, (r) The value of one revolution of the micrometer-screw de- pends of course upon the temperature at which the determi- nation is made. The range in temperatures at Carloforte and Ukiah is not sufficient to enable a gcKxl determination of the temperature coefficient to be made, and the observed values at the other stations depart rather widely from the theoretical values computed from the coefficients of expansion of brass and steel and the known values of one revolution of the screws. These differences are to be explained through the statement that the temperature coefficient evidently depends upon factors other than those just stated. All of the screws were investigated for both progressive and periodic errors, either by observation of polar stars at elonga- tion or by the use of auxiliary apparatus. Periodic errors of a sensible magnitude were found only for the instruments at Tschardjui and Carloforte. The screw of the Cincinnati telescope was found to be practically free from both progres- sive and periodic errors. The progressive errors of the screws at Carloforte and Gaithersburg were found to be considerably larger than the values obtained at Potsdam in tests applied before the instruments were shipped. The only explanation seems to be that the screws were damaged in some way during transportation. The values of the spaces of the latitude levels were deter- mined by micrometric settings upon the mire or by the use of a level-trier. At Ukiah a new method of observing stars of nearly the same declination was tried by Dr. Schlesinger with good success. This method has certain decided advan- tages and the details of it have already been explained in these Publications (Vol. XIII, p. 13). The effect of temperature and barometric pressure on the levels was not investigated. Astronomical Society of the Pacific, 147 Instrumental Errors. — Before making observations for lati- tude with a zenith-telescope it is necessary to so adjust the instrument that any instrumental errors which may remain shall be so small that they will not have an appreciable effect upon the accuracy of the results to be obtained. In order to attain this end the vertical axis must be made truly vertical, or very nearly so, the horizontal axis truly horizontal and in the plane of the prime vertical and the collimation zero, or rather of the same magnitude as the flexure of the horizontal axis, in order that the one may counteract the other, or that the collimation minus the flexure may be nearly zero. The position of the axes may be tested by means of the levels attached to the instru- ment and by the mire. The collimation, flexure, and position of the meridian targets can be tested only by observations of the stars for time. Since the telescope in this type of instru- ment is attached to one end of the horizontal axis and a counterpoise of equal weight at the other end, the flexure of the horizontal axis is large, about two seconds of time, and a time determination with this instrument involves a laborious process unless the flexure be assumed as a known quantity. Volumes I and II give the daily values of the instrumental errors for each station. Atmospheric Conditions, — Observations of the inside and the outside temperature and of the barometric pressure are made hourly during the progress of observations. The only use to be made of these would be in the investigation of pos- sible cases of abnormal refraction. It is the difference of the refraction of the two stars of a pair which enters into the computation of the latitude, and under normal conditions this may be computed for stars at small zenith-distances by means of a formula based upon a mean value of the temperature and the barometric pressure. In addition to the individual temperature and barometric readings there is given a tabulation showing the mean tem- perature for each group connection at each station. The great- est range, 3S°.6 centigrade, is at Tschardjui, the least at Carloforte and Ukiah, I3°.7 and 14° .8 respectively. The range m group-connection means is, trom — 8° to -[-21° at Mizu- sawa, from - — 9° to +26° at Tschardjui, from -j- 10° to -f 23° at Carloforte, from — 5° to +23° at Gaithersburg, from — 4° to + 24° at Cincinnati, from -f 4° to -V 19° ^^ « « 148 Publications of the Ukiah. At the last-named place, although the midday tem- perature often reaches 40° (104° Fahrenheit), and at times has reached as high as 45° (113° Fahrenheit), yet the temper- ature decreases rapidly immediately after sundown, and such a thing as a hot night is practically unknown. Results of Observations. — The individual values of the lat- itude from each pair observed, computed by means of the equation already given, are found in tabular form in this sec- tion. The total number of determinations made during the period covered by the first volume is 27,387. The percentage of nights upon which observations were obtained at the vari- ous stations is as follows : — Mizusawa 48 per cent. Tschardjui 33 Carloforte 70 Gaithersburg 48 Cincinnati 34 " Ukiah 47 " Average 47 per cent. The conditions at Carloforte, in the Mediterranean Sea, must be almost ideal from an astronomical standpoint, still the above tabulation cannot be taken as a true index of the weather at the stations. At Carloforte and at Mizusawa two observers are constantly employed, and probably nearly every favorable night is utilized. At the other stations, where all of the obser- vations are made by a single observer, many favorable nights must of necessity be allowed to pass. At Ukiah, for instance, the percentage could be increased by at least ten, perhaps fif- teen, if two observers were employed. In considering the above table the further fact should be taken into consideration that Professor Portkr, who makes the observations at Cincinnati, has many other duties in connection with his position as director of the Cincinnati Observatory and professor of astronomy in the University of Cincinnati. With him observing for latitude is an avocation and not a vocation. We should also consider the still -further fact that at some stations, — for instance, Mizusawa, — many nights are rendered incomplete by fog or clouds, and a night upon which only one pair is obtained enters into the above tabulation with the same weight as a complete night of sixteen pairs. During the 750 days since observations Astronomical Society of the Pacific. 149 were begun at the last station to start, Mizusawa, there were only five upon which observations were obtained at all six stations. Determination of the Definitive Latitudes. — The first inves- tigation undertaken under this heading was to determine whether or not there was a systematic difference between observations taken east-west and those taken west-east. None of significance was found except at Mizusawa, in November and December, 1900. Only the seventy-two latitude pairs were used in the definitive determination of the latitude. The next step was to determine corrections to the declina- tions of the stars from the observations themselves. There are two steps in this process, — first, to determine the reduc- tions to be applied to the results of each pair in order to reduce them to a mean declination system of the group; second, the detennination of the reductions necessar}' to bring the groups to a common basis. The first step was accomplished by taking the mean of the results from the six zenith pairs on each night that the complete group was observed, and then sub- tracting the individual results, including those for the two refraction pairs, from this mean. The results for each pair at each station were then collected and the grand means taken as the corrections to yi (8n + 8s) for each pair. The total mean error of the results will be made up of the accidental errors of observation and the systematic station errors, which last are either instrumental or personal, or per- haps of an external nature, such as anomalous refraction. The numerical value of the first of these, the accidental error of observation, may, on account of the richness of the observa- tional material, be computed from the individual observations of a pair, thus eliminating all consideration of the errors of declination. The mean error for a single observation of a pair is about ih o''.is. The total mean error of the station mean for a single pair is it o".o67 for the latitude pairs, and ±: o/'ogo for the refraction pairs. These values are greater than those to be obtained from the accidental errors alone, showing that there are in fact systematic station errors. It is not possible as yet to state what these are due to, but an examination of the ten pairs having the largest differences of zenith-distance seems to show that they may lie in errors in the assumed values of the micrometer-screws. 150 Publications of the The corrections to the group means were applied to the mean group latitudes and the results assembled on pages 121-125. From these, differences between the group results for each group connection were obtained for each station and the results collected. After the weighted means for the six sta- tions had been taken, it was found that their algebraic sum differed appreciably from zero. One explanation of this, and perhaps the most probable, is that the value of the constant of aberration used in the star-place reductions was in error. It was found that a correction to the aberration of + 0^.042 would cause the "Schlussfehler'' — closing error — to disappear. This would change the adopted constant of aberration from 2o".47o to 2o".5i2, a change which is confinned by other in- vestigations entirely separate from this. It might be stated here that the computations given in volume II cast some doubt upon the reality of this correction. From the group differences the corrections to each group were formed which are necessary to reduce the twelve groups to a common declination system based on the declinations of the seventy-two latitude pairs. From these reductions to a mean system and the reductions to the group means the final corrections to the declinations of each pair were formed and collected into a table (page 129). These corrections were then applied to the daily means at each station, and these then formed into the group combination means, the latitude pairs and the refraction pairs being treated separately. Determination of the Path of the Pole.* — The path of the pole was determined from the normal values of the latitude for each group connection. The first step in this process was to determine the mean value of the latitude for each station, and this was done by a method of successive approximations. The differences between the mean values and the individual mean group connection values were then formed and plotted with time as the x co-ordinate. A mean curve was drawn for each station and then the values of — o (<^o being the mean latitude of the station) were read from it for each tenth of a year, thus eliminating in a large measure the errors of observation. It was first assumed that the motion of the pole could be represented by an equation of the form, A = X cos A -|- y sin A, Astronomical Society of the Pacific. 151 in which A <^ = <^ — <^o> ^ the longitude of the place of observa- tion west of Greenwich, x and y the rectangular co-ordinates of the instantaneous pole in a system the origin of which is located at the position of the mean pole, the .r axis of which points toward Greenwich, and the y axis toward a point in 90° west longitude. The above equation may be derived easily from the following figure. Fig. I. Let O B be the direction toward any observatory in west longitude A, P the instantaneous position of the pole, and P' the foot of the perpendicular dropped from P upon 0 B, Then we have, O F' = A <^ = JIT sec A -j- (y — .r tan A) sin A, , ^ sin^ Ax, . . = X { sec A , ) + y sin A, ^ cos A ^ -^ = X cos A -j- y sin A. Early investigations showed that the observations were not satisfied very well by this equation, and Dr. Kimura suggested the introduction of a third unknown independent of the longi- tude, thus, A «^ = A- cos A + y sin A -f -J. Least-square solutions under both assumptions were made, the one involving the solution of six equations for two unknowns 152 Publications of the at each tenth of a year, the other the sohition of six equations for three unknowns at each tenth of a year. The sum of the weighted squares of the residuals is so measurably better under the second assumption that there seems to be no doubt about the existence of the term 2. The largest residuals were found in the case of Gaithersburg, and they were so much larger than the others that the case seemed to demand special inves- tigation. The period under discussion involved a change of observers at Gaithersburg, Smith leaving at the close of 1900. The two observers, however, did not observe together long enough to determine their personal equation. It was found that the large residuals at Gaithersburg could be greatly re- duced by assitwing a personal equation of a tenth of a second, — namely, <^ Davis — Smith = + o".io. Upon the introduc- tion of corrections based upon this assumption the residuals for Gaithersburg, and also for Cincinnati, were reduced to the same order of magnitude as those of the other stations. The difference between the results obtained by two observers lies perhaps not so much in the bisections of the stars as in the general handling of the instrument, especially, in the opin- ion of the reviewer, in the manipulation of the levels. The final values of x and y give the motion of the pole as represented in the first part of the curve of Figure II, reprinted from these Publications,^ and showing also the motion of the pole as obtained from subsequent observations up to the beginning of 1906. It is not possible to decide from the data at hand whether or not the values of s derived for these stations hold also for other latitudes. The question can be most easily decided by establishing latitude stations in the southern hemisphere, and this has now been done. Three explanations are offered by Dr. Albrecht in regard to the tenn c — anomalous refrac- tion, a north and south oscillation of the center of gravity of the Earth, the effect of the neglected annual parallax of the fixed stars. The values of c for the six different stations were found to be practically the same, so that the hypothesis of anomalous refraction seems to be excluded. Volume If. — The second volume contains the presentation of all the observations made between 1902, January 5th, and 1905, January 4th. The treatment in this volume is in all * Vol. XVIII, No. Tir, p. 315. Astronomical Society of the Pacific. 153 respects similar to that given in Volume I, except that the section on the description of the observatories is omitted and a section is added at the end under the heading, "Derivation and Discussion of the Results of the Refraction Pairs." It Cf?0 V ♦ a^ ^oTfO otoo " o"w -a'io ^ 1 1 1 1 t ^P X -^ r^ ^^**sJN^^ '9r» ^0 \\ \ ^cf^^J^ 6» -^ 9tl \ \ \ 99\ ib \\ A ^ 4ff- Olol 7 *M r \ •*w^ / lY I 50v.m( ? 3C) /A no 'Y y q? < os-Jj^f ^ • ^^^^^^ ^ ^^C^ ^ /^ J^u a'20 ■ ^^^^ "»^^v / t. , '^'^'^ „ 1 J 1 1 -azo -a 10 oToo - ♦ fl*f ^ - ♦a^^ ■►^./^ oloo Fig. IL -^^./^ '0^0 is intended to call attention here only to those points at which something new is brought out in the second volume. Additional observations were made at all of the stations for values of one revolution of the micrometer-screws, and an at- tempt was made to determine the temperature coefficients. As before stated, these were detennined at all of the stations except Carloforte and Ukiah, where the range of temperatures is not sufficiently great to enable a good determination to be 154 Publications of the made. Since all of the instruments were made by one maker, after the same pattern, differing only in size, it was decided to assume that the temperature coefficient was the same for all. From the observations for the four instruments for which determinations have been made, the weighted mean tempera- ture coefficient, the change per degree centigrade per second of arc of the micrometer-screw, was found to be — 0.0000259, and the resulting values for the six screws are then easily found. Before the final results for Volume II were worked out, corrections to the observed values of one revolution of the micrometer-screws were determined from the latitude obser- vations themselves. These corrections lie between — 0.0009, for Gaithersburg, and — 0.0251, for Tschardjui. The total number of observations obtained during the period under consideration in the second volume is 36,173. The percentage of nights upon which observations were made is 46.5, almost exactly the same as during the period covered by \'olume I. There was an increase in the percentage at four of the stations and a decrease at Gaithersburg and Cincinnati. The percentage at Carloforte increased from 70 to 73. During the interval under consideration, 1,096 days, there were only fourteen evenings on which observations were ob- tained at all six stations, and on three of these only one pair was obtained at some stations. There was not a single evening on which a complete programme was obtained at all six sta- tions, and bv lookin^: back into \'^olume I it is found that there has not been a single night, from the time the last station started, 1899, December i6th, to 1905, January 4th, 1,846 nights, upon which a complete programme was obtained at all six stations. This seems a little strange at first thought, but a simple computation according to the principles of probability will show that we are here dealing with a very rare event. Let us ask, first. What is the probability of obtaining at least some observations at each station on the same night? If we assume that observations are made on the average on fifty p)er cent of the nights, then the probability of obtaining observations at any one station on any particular night will be one half, and manifestly the probability of obtaining observations at two stations on the same night will be 3/2 X /4, or 54» and the probability of obtainiug observations at three stations on the Astronomical Society of the Pacific, 155 same night ^ X /^ X ^2, and the probability of obtaining observations at six stations (y^)^ = y^^. Observations would therefore be made at all six stations on the same night on an average of once in every sixty-four nights. Our assumption, however, that observations are made upon fifty per cent of the nights is somewhat in error, the true percentage being almost exactly 46.5. The probability of this event occurring would be therefore (***°/iooo)** which equals Voo- This event would occur on an average therefore of once in every ninety-nine days, or nineteen times during the 1,846 days under considera- tion.^ This result is in exact agreement with the observed .number: there were five such events during the period cov- ered by \^olume I and fourteen during the period covered by Volume II. (r) Let us now ask, What is the probability of obtaining a com- plete night's work at all six stations on any particular night ? The ratio between the number of complete nights and the total of nights observed is not given in the volumes, but it is proba- bly not far from one half. At Ukiah about sixty per cent of the nights upon which observations are made are complete, but the percentage is known to be less at some of the other stations. If now we assume that observations are made upon fifty per cent of the nights, and fifty per cent of these are complete, then the same kind of reasoning that was used before will bring us to the conclusion that the probability of the occurrence of the event under consideration is ( V.^)" = V4oo6- That is to say, a complete night's work will be obtained at all six stations on an average, in round numbers, of once in every 4,000 nights, or once in about eleven years, so that it is not at all surprising that this rare event did not occur at all during the first five years of observations, (r) The mean errors of a single determination of the latitude are practically identical for all stations except Carloforte, which seems to show that as accurate observations can be made with the small instruments at Tschardjui and Cincinnati as with the larger ones. The observations made at Carloforte stand in a class by themselves, as far as accidental errors go, these being distinctly less than at the other stations, probably largely * The exact method of computing this probability is, of course, to take the product of the six separate probabilities rather than the sixth power of the average probability. The result comes out sixteen, rather than nineteen. 156 Publications of the due to the favorable meteorological conditions. An examina- tion of the curves represented in Figure 3 shows, however, that notwithstanding the small accidental errors and the large number of observations obtained at Carloforte the final results for this station are not as accurate as for some of the other stations, — Mizusawa, for example, — where the taking of ob- Vaiaji^drrfkflh/fhe.aitfdtgveinxdnai.Slaiionm.. ^- iCm' «** •O u U ^* m-m Fig. III. Astronomical Society of the Pacific. 157 servations is often badlv interfered with on account of clouds or fog. Nearly twice as many observations are obtained at Carloforte as at Mizusawa, and this is a good illustration of the precept that little or nothing is to be gained by increasing beyond a certain moderate amount the number of observa- tions made with the same instrument under similar circum- stances. Perhaps just as good results could be obtained by limiting the number of observations at each station to 1,200 or 1,500 a year, (r) In explanation of Figure III it should be stated that the small circles represent the average observed latitude for cer- tain intervals, the small numbers adjacent to the circles indi- cating the number of observations entering into the average. After the results were all combined and the most probable values of x, y, and s were obtained from the least-square solutions, as already explained, the values of x and y were computed for each station at certain times and the results plotted on the same figure with the observed curves, produc- ing the smooth curves of Figure III. The amounts by which the circles depart from the smooth curves, the residuals, are probably very close to the true errors of observation, and that station in which these residuals are the smallest has, of course, procured the best results. The "closing errors" vary so much more in the different years for the same station than should be expected from the accidental errors, that it seems necessary to conclude that these differences cannot be all laid up to an erroneous value of the aberration constant. It would be necessary to assume the constant of aberration equal to 2o".54i in order to com- pletely explain away the closing errors. The differences are perhaps due to meteorological causes, — a very handy explanation. The quantities s, as derived in the second volume, show a tendency toward a change in a positive direction, which pre- sumably is due to uncertainties concerning the knowledge of the proper motions of the stars observed. An average change of + o".oi6 a year in the proper motions would cause the positive tendency in z to disappear. The evidence seems to show that we have in this quantity s a term of constant ampli- tude and a period of a year. The observations thus far, however, give no indication of the cause of this term. \ 1 58 Publications of the Astronomical Society, &c, \''olume II is concluded with a discussion of the results obtained from the observations of pairs at large zenith-dis- tances, the so-called refraction pairs. Several hypotheses concerning abnonual refractions were made, but no very defi- nite conclusions concerning them could be drawn from the data at hand. Without taking up the details it is perhaps sufficient to state the general conclusion reached by the authors, and that is, that observations at 60° zenith-distance provide no evidence whatever from which conclusions can be drawn re- garding refractive perturbations at small zenith-distances. The observation of refraction pairs was therefore discontinued at the bes^inninsr of 1006. ^ t^ r,^ ^ Sidney D. Towxley. ES FROM PACIFIC COAST OBSERVATORIES. The Resi'lts ok am Effort to Determine Motion within THE Solar Corona.' I The existence of material in the corona, at various distances Jrom the Sun, implies that it has come from somewhere, no iibt verj- largely, or even almost exclusively, from the Sun If. The changed coronal forms and structures observed different eclipses are further evidence that motion occurs. Is the material moving out from the Sun, or toward the Sim, both? Accurate observational knowledge on this subject |ls very meager. At the eclipse of 1901, favorable conditions existed in the iSorona for determining velocities. Measures of short-exposure [•egatives taken near the beginning and end of totality by the iiCrocker Expedition to Siimalra showed no displacements of fioronal masses in tlie interval of a little more than five ■jninutes.' Considering the accuracy of measurement, a velocity of enty miles per second across the line of sight should have letected with certainty, and motions should have been ispccied had they been as great as twelve or fifteen miles iper second. The unusually favorable eclipse of August 30, 1905, afforded \t hope that large-scale photographs of the corona secured in ibrador. Spain, and Egypt, or in two of these countries, puld enable us to detect changes in the coronal structure irring in the long intervals between the times of totality those countries. Such photographs were obtained by the TOckcr expeditions to Spain and Egypt, cloudy weather hav- tag prevailed in Labrador. The Spanish plates were secured l>y Messrs. CaSipbell and Perhine, with the assistance of Or, R. S. DuciAN and Professor Felipe Lavilla ; and the Lift Obierrttar j i6o • Publications of the Egyptian plates by Professor Hussey, with the assistance of the late Professor Robert H. West and Mr. H. T. R. Dray. Totality occurred seventy minutes later in Egypt than in Spain. We have made careful comparison of the coronal images obtained at the *:wo stations. A number of fairly well-defined nuclei existed both east and west of the Sun. Details of structure within the nuclei appeared to change, but the nuclei as a whole seemed to remain in the same positions. Meas- ures of great accuracy cannot be made, principally because the poorer seeing in Egypt affected the definition ; but we are able to say that the masses in question could not have moved so much as one mile per second during the interval of 4,200 seconds. Greater speeds might well have occurred within the principal coronal streamers, or within some of the arched forms which inclose prominences, without our having detected them ; for their structure is quite uniform, and well-defined nuclei are absent. Thus, in the structures where higher speeds should perhaps be most naturally expected, photographic methods have little chance to detect them. However, it is not imi)robable that at some future eclipse well-defined nuclei in coronal streamers will exist and be recorded at two or more stations. Our result is in harmony with Arriienius's view of coronal origin: "It is very probable that those drops for which gravi- tation is just compensated by the pressure of radiation will be the chief material of the inner corona. For drops of other sizes are selected out, the heavier ones by falling back to the Sun, the lighter ones by being driven away by the pressure of radiation, so that the drops which, so to say, swim under the equal influence of gravitation and pressure of radiation will accumulate in the corona/'* Assuming that motions of appreciable size exist within the corona, it should be said that the spectrographic method of determining them is unpromising, for several reasons. The exposures are from necessity short, and the coronal light is intrinsically weak. The brighter parts of the corona radiate light forming a continuous spectrum, neglecting the almost insignificant component which gives rise to bright lines, and the relatively small quantity of reflected photospheric light. * Arrhenius, Lick Observatory Bulletin, Vol. II, 190, 1904. Astronomical Society of the Pacific. i6i Spectrograms of the middle and outer corona, obtained with a relatively wide slit and low dispersion, record the Fraunhofer lines but faintly. A spectrogram of good strength would probably be difficult and uncertain in interpretation, as the slit of the spectrograph would receive light from streamers which radiate in a variety of directions from the Sun. Recalling that a reflecting particle moving directly from the Sun toward the observer will not displace the spectrum lines at all; that a reflecting particle moving directly away from, or directly toward, both Sun and observer, will give double displacement of the lines toward the red or toward the violet, respectively ; and that the coronal light falling upon the slit is from particles possessing a great variety of motions between these limits; the complexity of the result is evident. All the spectrographic measures of motion within the shal- low gaseous stratum giving the bright lines are likewise in accord with Arrhenius's theory. w. W. Campbell, March, 1907. C. D. Perrine. Note on a Disturbed Region in the Corona of August 30, 1905.^ The large-scale photographs of the corona of August 30, 1905, secured by the Crocker expeditions to Spain and Egypt, show an extensive region in the southeast quadrant composed of prominent streamers which appear to radiate from a com- mon point. The space-form of this region seems to be approximately conical. The apex of the cone, projected upon tlie photographic plate, is some distance within the Sun's limb. The apex no doubt is in or near the photosphere, and the apparent axis of the cone is directed radially out from the Sun's edge. This conical volume is similar to but not so prominent as that recorded in the corona of May 18, 1901? The chromospheric layer in the region crossed by these projected streamers is not very deep, nor does it show special activity. The streamers probably originate far from the limb ; but whether on the nearer or further hemisphere of the Sun is uncertain. The estimated points of intersection of the streamers (produced) were marked on the glass side of the Spanish negatives, Nos. 2 and 7, which were exposed at about 8» and 3" i6», respectively, after the beginning of totality. 'From Lick Observatory Bulletin, No. 115. 1 62 Publications of the The positions of these points were measured independently by klS^ *Tl«bV>l>J| «AkJ XVJkV^I 1* SJ I Position angle Distance from from Moon's center. Moon's limb. Observer. Negative No. 2 13!/^° 3'-24 w. w. c. Negative No. 7 i33>4 3-24 w. w.c. Negative No. 2 132 2.97 C. D. p. Negative No. 7 132^2 3 -11 CD. p. positions to the center of the Sun we have : — Co-ordinates of Apex of Disturbed Area. Position angle Distance from from Sun's center. Sun's center. Observer. Negative No. 2 134° i2'.78 w. w. c. Negative No. 7 i3i>^ 13-68 w. w. c. Negative No. 2 134 12.51 CD. p. Negative No. 7 131 1398 CD. p. An examination of the photographs of the Sun taken at Mt. Hamilton on this date shows a spot of medium size, sur- rounded by faculae, in the southeast quadrant, near the Sun's limb. The following position was determined from the nega- tive exposed at 4'^ 49"^ G. M. T.. August 30th, or 3^ 34™ after the coronal photographs were made in Spain. Position angle of spot 140^ Distance from Sun's center 12'. 6y The series of i)hotographs of the Sun taken at Mt. Hamilton for study in connection with eclipse problems extends from August 23d to September 11, 1905, inclusive. During this interval there was no other spot in the southern hemisphere. The lack of agreement in position of the apex of the dis- turbed region and the sun-spot at the time of the eclipse, osition- angles of the spot when at 2'. 6 from the Sun's eastern Hmb have been determined as follows : — Astronomical Society of the Pacific, 163 1905. July 28 122° Farther side of Sun. Aug. 3 1323^2 Nearer side of Sun. Aug. 24 129J/2 Farther side of Sun. -^ug. 30 140 Nearer side of Sun. It is a question whether such disturbances of coronal matter have their origin in sun-spots or in the faculae surrounding the spots. It would be interesting to know the times of greatest activity of the spot group in question, but the history of its development is not known to us. The most probable date of the disturbance was August 3d, when the sun-spot was on the nearer side of the Sun. On that date the spot had the same position as the apex. On August 24th, with the spot on the farther side of the Sun, the position-angles of the spot and apex differed 3°. The form of structure within the disturbed region may be divided roughly into two classes : long, slightly curved stream- ers, and flocculent masses. The streamers contain no con- densations or other details of structure capable of accurate measurement, as a basis for determining the velocities of the matter composing them. If the forms of the streamers are functions of the velocities within them, as considered by Pro- fessor ScHAEKERLE, the spccd in question would be as great as several hundred miles per second. A determination of the velocities of some of the flocculent masses near the limb, on the assumption that August 3d was the date of their ejectment, gives a value of 700 feet per second as the minimum radial speed. The masses farther from the limb would require velocities perhaps five times as great in order to carry them to their positions at the time of the eclipse. These results are in accordance with the conclusions based on velocity detemiinations during the interval of seventy minutes between the occurrence of the eclipse in Spain and Egypt. This determination showed that the velocity of the flocculent masses could not have been over one mile per second. April, 1907. ^^'- ^^'- Campbell. C. D. Perrine. Results of the Search for an Intramercurlvl Planet AT the Total Solar Eclipse of August 30, 1905.^ Owing to the existence of thin clouds during the eclipse of 1901 in Sumatra, the search for an intramercurial planet was 'Abstract from L. O. Bulletin. No. 115. 164 Publications of the not as complete as desired. It was made practically certain that there was no body as bright as the 5th magnitude in the region where such a planet would probably be, if one existed.* The eclipse of August 30, 1905, offered unusual advantages for continuing the search. It was possible to occupy three widely separated stations ; the eclipse came at a season of the year when the chances for clear weather were excellent at two of these stations, and the duration was longer than the average. The value of observations at two or three stations, in case a planet should be found, would be very great, for they would enable some idea of the orbit to be obtained. With an obser- vation at only one epoch, nothing of the orbit could be learned, and subsequent re-observation would be very difficult. In any case, the determination of the orbit of such a body, from the infrequent observations that could be secured at eclipses, would present unusual difficulties. It was therefore planned that each of the three expeditions, despatched through the generosity of Mr. Wm. H. Crocker, should be equipped with four photographic telescopes designed for efficiency in this problem. With a few minor exceptions, the plans for securing the necessary photographs at each of the three stations were sim- ilar to those of 1901, which are fully detailed in L. O. Bulletin, No. 24. The only exceptions of importance were the restric- tion of the field to be searched, and the taking of the duplicate exposures at different times. The fields covered were 29° X 9® in the Spanish cameras, and 25° X 8J4° in the Labrador and Egypt cameras, the longer axis being parallel to the Sun's equator, as in 1901. The Sun was in the center of these regions. The programme was carried out as planned at Alhama, Spain, and at Aswan, Egypt, although at the Spanish station there were thin clouds during all of totality. The four cam- eras at Cartwright, Labrador, had been made ready by Dr. Curtis, but unfortunately the sky was densely clouded, and no observations were possible. A hasty examination of some of the Spanish plates, at the station, revealed so few star images that the work was dis- continued until the return of the expedition to Mt. Hamilton. A careful examination revealed the images of thirty-six stars ^L. 0. Bulletin, Vol. I, 183, 1902. Astronomical Society of the Pacific. 165 on the Spanish plates and nineteen stars on the Egypt plates. The fewer stars on the Egypt plates is explained by adverse conditions which overbalanced the effect of the thin clouds at the Spanish station. All of the objects found were identified as known stars. The average faintest visual magnitude of the stars shown is 8.0. Assuming that the average planetary body would be one mag- nitude fainter photographically than the faintest stars on the plates, then any planet of 7.0 visual magnitude should have been recorded on our photographs. This conclusion is somewhat more far-reaching than could be drawn from the 1901 eclipse results and tends to confirm the belief that some other explana- tion must be sought for the peculiarities in the motions of Mercury. The recent investigations of Seeliger on the effect of the matter concerned in the zodiacal light upon- the inner planets seem to show that the observed outstanding perturbations in the motions of Venus and Mars, as well as those of Mercury, can be sufficiently accounted for upon a reasonable assumption of the distribution of such matter about the Sun. Should this explanation be confirmed, the only further need to continue the intramercurial search will be for the purpose of determin- ing whether there are any asteroidal bodies in that region. A considerable number of such bodies might exist without their combined mass being sufficient to produce appreciable disturb- ances in the motions of the planets. v^. iJm X ERRIr«E. Note on Comet h 1907 (Mellish). A telegram announcing the discovery of a new comet by Mr. Mellish, at Madison, Wisconsin, was received here on the afternoon of April 15, 1907. Observations were secured by the writer with the 12-inch telescope on the nights of April 15th, i6th, 17th, and 29th, and with the 36-inch on April 30th and May 7th. On the first three nights the comet was visible in the 3-inch finder, though faint on the third night on account of increasing moonlight. It was, however, a difficult object to measure because of its diffuseness and irregularity of out- line. Examination with the 36-inch telescope on April i6th showed a broad fan-shaped tail in the south-preceding quad- rant that could be traced about 6' from the coma, yjVvVcJcv 1 66 Publications of the appeared to be roughly circular and less than 2' in diameter. There was no well-defined condensation. By May 7th the comet was too faint to measure with the 12-inch telescope. A rough comparison with the ephemeris in A, N. 4172 gives the residuals (O-C) for May 7th, + 18* ""^' + ''-S- R. G. A.TKEX. May 24, 1907. Visual Obskrvations of Comet 1905 IV. A note in No. 113 of these Publications (p. 88) calls atten- tion to the reobscrvation, photographically, on March 21, 1907, of this comet, which was originally discovered by Kopff ill March, 1906. Unfavorable weather conditions prevented my looking for the comet with the 36-inch refractor until the night of April 20, 1907, when it was readily seen. Though it was hardly as bright as a I4th-magnitude star, it was not a very difficult object to measure, because it had a well-defined nucleus of about 15 J/ or i6th magnitude. A second observation w'as secured on May 4, 1907, and a comparison of the two with Weisse's ephemeris in A. N . 4166 shows that the observed motion is slightly more rapid than the predicted. ^^ ^ . * R. G. AlTKEX. May 24, 1907. Note ox Comet a 1907 (Giacobixi). From four observations (March 9th. by Giacoiuxi, at Nice; March I3tli, April 3d. by Fatii, at Mt. Hamilton: April 9th, by Aitkex, at Mt. Hamilton) a second orbit of Comet a 1907 has been computed under the direction of Professor Crawford. The fourth observation was introduced into the computation by the formation of a fictitious third position based on the two April observations. The four observations are satisfactorily represented by a parai)ola. The inclination of the plane of the orbit to that of the ecliptic is 141° 39'; the longitude of the ascending node is 07° 30'; the longitude of perihelion is 54^ 21'. The perihelion distance is 2.05 a'^tronomical units, and the time of perihelion passage is March i(), 1907. The elements and an ephemeris extending to the end of ^lay are published in Lick Obscrraiory Bulletin, No. 113. The comet is moving away Astronomical Society of the Pacific, 167 from both the Sun and the Earth, and it is following the ephemeris very closely. Sturla Einarson, Berkeley Astronomical Department, ^^* ^STELLE ULANCY, May 19. 1907. Ar.iCE JOY. Note ox Comet c 1907 (Giacobixi). A preliminary orbit of Comet c 1907 has just been com- pleted as this number of the Publications is going to press. The three observ^ations used were made June 1st, 3d, and 4th, by Giacobini at Nice, Hammond at Washington, and Aitken at Mt. Hamilton, respectively. The elements and an ephemeris are given in Lick Observatory Bulletin, No. 116. The obser- vations are represented by a parabola. The inclination of the orbit plane to the ecliptic is 16° ; the longitude of the ascending node is 161°. It was nearest to the Sun on May 27th, at whicli time it was 117,000,000 miles distant. The comet is faint and is receding from both the Earth and the Sun. At present it is east of the sickle in Leo. It is traveling toward pLeonis, and on June 21st will be about 5° due north of it. Berkeley Astronomical Department, bTURLA ILIN.VRSON, June 5, 1907. EsTELLE Clancy. Plans for Observing the Total Ecf.ipse of January, 1908. Arrangements have been completed to dispatch an expedition from the Lick Observatory to observe the total solar eclipse of January 3, 1908. The Moon's shadow will cross the central Pacific Ocean from west to east, and pass over only two known islands. One of these is Flint Island, in longitude 151° 48' W. and latitude 11° 26' S., — that is, about 390 miles northwest of the island of Tahiti. The eclipse will occur at 11:18, local mean time, with the Sun at zenith-distance 15°. The duration given by the Ameri- can Ephemeris will be 4™ 6^ The generosity of Mr. Willl^m H. Crocker has made pos- sible the sending of the expedition. The expedition will sail from San Francisco on November 22d for Tahiti. The problem of transportation from Tahiti to Flint Island and return was a difficult one, but the interest of the Navy Department of the United States Government was enlisted, and the U. S. gunboat "Annapolis" has been detailed to meet the expedition at Tahiti, transport it to Flint Island, 1 68 Publications of the Astronomical Society, &c. re-embark the expedition after the eclipse, and return it to Tahiti. The "Annapolis" is stationed regularly at Pago-Pago, island of Tutuila, and will be in personal command of his Excellency, Governor Moore, of Tutuila, while on eclipse duty. A later statement will describe the personnel and scientific plans of the expedition. It seemed to me very important that the scientific programme should include a bolometric survey of the solar corona, similar to that inaugurated by Professor Abbot at the eclipse of 1900. There is certainly no one more competent to undertake this survey than Mr. Abbot himself. Accordingly, I brought the subject and the arrangements outlined above to the attention of Secretary Walcott of the Smithsonian Institution and Di- rector Abbott of the Astrophysical Observatory of the Insti- tution, and they have been so good as to plan for an expedition to secure the bolometric observations. The two expeditions are essentially independent, scientifically, but are united in travel- ing and subsistence arrangements. ^V. W. Campbell. Changes in the Lick Observatory Staff. Mr. James D. Maddrill, Fellow in the Lick Observatory during ihe past four years, received the degree of Doctor of Philosophy from the University of California in May, 1907. His thesis relates to a photometric and spectrographic study of a number of well-known variable^ stars of the 8 Cephei type. An abstract of the thesis will be found in a later number of these Publications. Dr. Maddrill has been appointed astron- omer in charge of the International Latitude Observatory at Ukiah, California, in succession to Dr. S. D. Townley. Mr. J. C. Duncan, former Fellow in the Lowell Observa- tory, and at present Instructor in Mechanics and Astronomy in the University of Indiana, has been appointed Fellow in the Lick Observatory for the year 1907-1908. W. W. Campbell. Applications. Applications are desired for the position of Assistant in the Lick Observatory, and for the position of Fellow in the Lick Observatory. For particulars, address The Director. W. W. Campbell. GENERAL NOTES. Mutual Occultations and Eclipses of the Satellites of Jupiter in ipo8. — At the meeting of the Royal Academy of Sciences of Amsterdam on October 27, 1906, Professor J. A. C. OuDEMANS presented a paper on '*The Mutual Occultations and Eclipses of the Satellites of Jupiter in 1908." A short account of the paper may be of general interest, as the phenom- ena can be observed by any one possessing a telescope. The orbits of the four larger satellites of Jupiter lie in approximately the same plane. When the Earth is in or near this plane the satellites would appear to move forward and backward along a straight line, thus occulting one another in passing. In the same way, when the plane of the orbits passes through the Sun, there would be mutual eclipses of the satel- lites. The orbital plane passes through the Earth and the Sun twice in each revolution of the planet, so that these phenomena occur at intervals of about six years. The plane passes through the Sun on April 25, 1908, and through the Earth on July 8th of the same year, so that near these times the respective obser- vations may be made. Some difficulty may be experienced in making the observations near the latter date as Jupiter will be at a low altitude, passing to conjunction with the Sun on August 17th. Up to the present time but few such occultations have been observed, and there is only a single recorded instance of mutual eclipse. For this reason the observations of next year will have a special interest, and their value will lie in furnishing data to correct the elements of the satellite orbits. If these orbits all lay in exactly the same plane, mutual eclipse would occur at each heliocentric conjunction of two satellites near the time named, and similarly mutual occultation at each geocentric conjunction. As this, however, is not the case, some of the conjunctions will occur without bringing about either eclipse or occultation. In the latter case those using micrometers can make observations of value by measuring the difference in declination at the time of conjunction. The following list is taken from a table given by Professor OuDEMANS, and contains the occultations and ecVipses V\sJv\Afc lyo Publications of the at the Lick Observatory. This will serve for the Pacific Coast States. In observing it will be well to begin before the com- puted time and watch the progress of the phenomenon as the times given are for central eclipse or occultation. Time 1908. of Eclipse. Pacific S. T. Eclipwd SaMllite. Eclipsing Satellite. Direction from Jufittr. April 2 lO^ 1 3m I Ill East 3 8 26 IV I West 4 8 ^2 IV II East 4 9 21 I II East 5 II 56 III II West 6 12 12 III I East 9 12 52 I III East II 7 42 II IV East II II 43 I II East II 12 24 I IV East 22 7 13 IV II East May I 9 5 II III West 1 10 43 II I East 5 9 57 III II East 6 8 38 I II East lO 8 41 I II West II 26 III II West 13 II 31 I II East 17 8 9 I II F-ast Time of Conjunction. 1908. Pacific S. T. Occulted Satellite. Occulting Satellite. Direction from Jufittr. :\[ay3i & 46" I II East June 8 7 57 IV II West 9 y 1 [8 III I West 29 7 50 I II West July II 6 t ;7 II I West March 7, 1907. E. A. Path Recent Double-Star Obsen'ations. — In Part 3 of Volume X of the Publications of the Washburn Observatory, Professor Gkor(,e C. Com stock publishes the results of his observations of double stars in the years 1897- 1906, "i^de with the 15-inch refractor. The measures are arranged in the same form as those previously published by the same observer in Part i of \'olume X, and constitute with them a homogeneous series. Astronomical Society of the Pacific, 171 It is a pleasure to examine this publication, for the observ- ing list has been carefully selected, including only stars in need of measures; the stars have been observed systematically, and llie results are arranged in convenient fomi for the use of investigators, with no superfluous matter. It is to be hoped that his many other investigations will not prevent Professor CoMSTOCK from continuing with his double-star observations. A volume of quite different character is one entitled **Meas- ures d'Etoiles Doubles faites a i'Observatoire de Qievreuse de 1904 a 1906, par Maurice Farman." The exterior of the volume leads one to infer that M. Farm an was a most indus- trious observer, for it is a quarto publication of 128 pages. Examination shows, however, that M. Farman's own observa- tions occupy only one line for each star, the remaining lines — half a column in many cases — being devoted to a resume of other observers' results between the years 1875 and 1895. As the observing list is drawn almost exclusively from the lists of Struve, Otto Struve, and Burnham, of which we possess catalogues giving practically complete histories of each star to the present time, it would seem that the space thus occupied in the present volume could have been used to better advan- tage by giving the observer's own results in more detail. As it is, he gives only the distance, angle, and date, without any information as to the numl:)er of nights the pair was observed, the atmospheric conditions, the hour-angle, or the accordance of the measures. It is stated in the introduction that each posi- tion-angle is the mean of five settings, and each distance the mean of ten double-distance measures, and it is perhaps to be inferred that each star was observed on one night only. The measures were made with a refractor of 0^.24 aperture, and an eye-piece magnifying about 500 diameters. R. G. A. Eros Comparison-Stars and the Magnitude Equation. — In Number in of these Publications a brief note was printed calling attention to Dr. Fritz Cohn's investigation of the reference-stars used for the observations of Eros. Dr. Coiin concluded that the photographic determinations of the posi- tions of these stars at several observatories show a decided magnitude equation. In a later number of the Astronomische Xachriclitcn, Professor Hinks. of Cambridge, England, who has made a very thorough study of the Eros comparison-stars, 172 Publications of the controverts this conclusion and gives his reasons for thinking that whatever other systematic errors may inhere in the photo- graphic method, these particular observations are free from this special error. A very interesting discussion of the whole question has thus arisen, and a number of articles on the sub- ject may be found in the Astronomische Nachrichten, the Monthly Notices R, A. S,, and other journals, the outcome of which capnot yet be stated. It has long been known that practically every meridian ob- server has a personal equation due to magnitude, — ^that is, that he observes the transit of bright stars relatively too early as compared with the transit of fainter stars. Careful observers usually determine the amount of this equation by a series of special observations in which the transit of bright stars over half the field is observed at full brightness, and over the other half through a screen placed before the object-glass which reduces the brightness several magnitudes. It has been claimed, and Dr. Cohx assumes in his argument, that observa- tions with the Repsold self-registering transit-micrometer are free from this systematic error. The questions at issue can only be decided by careful investigations by expert observers. To the amateur perhaps the most interesting feature of the whole discussion is the minuteness of the quantities involved. It is another illustration of the high standard of precision that modem astronomy sets for its followers. Probabilities. — If any of the readers of these notes are en- gaged in teaching the theory of probabilities to classes in algebra or the method of least-squares, they may be interested in the example given on page 155 of this number. The text- books contain plenty of examples, but they are usually "made- up" ones. The writer has often thought that a few real examples, showing that actual results do come out in practical agreement with those computed by theory, would be very helpful in presenting this subject. The computations employed in the example just referred to may be used in considering other programmes of work which are dependent upon the weather. For instance, suppose a proposition is made to establish a number of astronomical stations, widely separated along the path of totality, for the purpose of observing changes in the outer envelopes of the Sun Astronomical Society of the Pacific. 173 during the progress of a total eclipse of that body. The ques- tion naturally arises, What is the probability of the skies being clear at all of the stations on eclipse day? In order to give concreteness to the problem, let us suppose that it is equally likely to be clear or cloudy at any station, which is not far from the true state of affairs for most localities, then the probability of obtaining clear sky at any particular station is one half. The probability of obtaining clear skies at any two stations (separated sufficiently so as not to be under the same local weather conditions) is the product of their separate probabilities, or one fourth; of three stations, one eighth; of four stations, one sixteenth ; of five stations, one thirty-second. If, then, some problem should be proposed which depends for its solution upon observations to be made at five widely sepa- rated stations upon the same day, it is seen that it would be utterly foolish to expend money for this purpose, because there would be only one chance in thirty-two of obtaining the re- quired observations. S. D. T. Notes from "Science" — Professor John Krom Rees, since 1881 professor of geodesy and astronomy and director of the Observatory of Columbia University, died on March 9th, in his fifty-sixth year. Professor Rees had been ill for several years and had recently been made Professor Emeritus. Professor Henry Davis Todd, U. S. N. (retired), died at Annapolis, on March 8th, at the age of sixty-nine years. Pro- fessor Todd served through the Civil War with distinction, and became head of the Department of Physics and Chemistry at Annapolis in 1878. From 1886 to 1899 he was assistant on the Nautical Almanac, and was director from 1899 to 1900, when he retired. The death is announced of Mr. Henry Chamberlain Rus- sell, F. R. S., government astronomer of New South Wales since 1870, at the age of seventy-one years. The New York Assembly on March 5th passed the Young Bill, which provides for the establishment of a nautical mu- seum and observatory in Bronx Park, New York. Dr. George E. Hale, director of the Solar Observatory of Mt. Wilson, has been elected one of the alumni members of the corporation of the Massachusetts Institute of Technology. Mr. C. G. Abbot, who had been for a number of years Sec- 174 Publications of the retary Langley's principal assistant in the Astrophysical Observatory of the Smithsonian Institution at Washington, and latterly its acting director, has been appointed director of the observatory, and Mr. F. E. Fowle, Jr., hitherto junior assistant, has been appointed aid. M. Henri Poincarie has been appointed a member of the council of the Observatory of Physical Astronomy at Meudon, in the room of the late M. Moissan. Funds have been donated by Mr. William C Sproul, State Senator, of Chester, Pa., for the purchase of one of the largest telescopes on the Atlantic Coast for Swarthmore College. The exact amount of the gift, or the size of the telescope, is not known, but the instrument will be quite as efficient as the Government's telescope at Washington or the University of Virginia's telescope at Charlottesville, which are the two larg- est instruments in the East. The telescope will be in charge of Dr. John A. Miller, professor of mathematics and astron- omy. Senator Sproul is a member of the board of managers and has been active in the management of the institution since his graduation, in 1891. Dr. H. C. Vogel, of the Astrophysical Observatory at Pots- dam, has been awarded the Maximilian order for art and science of the Bavarian government. Professor David P. Todd, of Amherst College, sailed on the *Tanama'' on May nth for Colon, Panama, Callao, Peru, and Iquique, Chile, in charge of the Lowell Astronomical Expedi- tion to the Andes, sent out by Professor Percival Lowell, of Boston. Mr. E. C. Sliphkr is photographer, Mr. A. G. Ilse, of Alvan Clark & Sons, the instrument maker, and Mr. R. D.' Eaglesfieli), mechanician. The party will observe the opposi- tion of Mars with the 18-inch telescope of Amherst College (Observatory, and the annular eclipse of the Sun, July loth, for Professor Newcomu. Abstracts of Papers. — Two recent numbers of Science, April 1 2th and 17th, contain accounts of the meeting of the Astro- nomical and Astrophysical Society of America, held in New York during the last convocation week in connection with the annual meeting of the American Association for the Advance- ment of Science. Thirty-one papers were presented before the society and four papers upon astronomical subjects before Astronomical Society of the Pacific. 175 Section A of the Association. If we may judge from the titles, many of these papers must have been very interesting. Ab- stracts of most of them may be found in the numbers of Science just referred to. The American Astronomer. — In a recent issue attention was called to the Journal of the Royal Astronomical Society of Canada, a new periodical, published bi-monthly,- and similar in scope to our own Publications, the Journal K, A. A., and others designed to extend and popularize the study of astron- omy. The second number meets the expectations raised by the initial issue, and we trust the Journal has entered upon a long life of usefulness. A publication of a different type is ''The American Astron- omer, an international publication for practical astronomers," published at Marlborough, Mass., of which two numbers have appeared. The object of this journal is to give prompt intel- ligence of items of interest to astronomers, and it is therefore the aim of the editor, Wm. D. McPherson, to publish as often as possible. At present the paper will appear monthly. It is an experiment worth making, and the result will be watched with interest. The subscription price is placed at $2.00 per year. 'How to Know the Starry Hcaz^ens." — We are glad to note that this work on popular astronomy by one of the members of our Society, Mr. Edward Irving, has been well received by the public. Very favorable comments have been printed in many journals, like the Outlook, that notice scientific books likely to interest the general public. Mr. Irving's facts are correct, his style free from technicalities, and his illustrations numerous, well chosen, and well-executed reproductions from excellent modern photographs and drawings. NEW PUBLICATIONS. Farman, M. Mesiires d*etoiles doubles. 1904-06. Paris: Gauthier-Villars. 1907. 4to. VII + 128 pp. Cloth. Hagen, J. G. Atlas Stellarum Variabilium, Series IV. 4to. Atlas and catalogue. Cloth. 120 Marks. Hale, George E., and Kent, Norton A. The spectrum of the high-potential discharge between metallic electrodes in liquids and in gases at high pressures. Chicago: Publications of the Yerkes Observatory. Vol. Ill, Part II. 1907. 4to. 38 pp. 8 plates. Paper. Haynes, E. S. The variable RS Cassiopeia*. Columbia: Uni- versity of Missouri. (Laws Observatory Bulletin, No. II.) 4to. 14 pp. Hill, G. W. The collected mathematical works of. Vol. IV. Washington: Carnegie Institution. 1907. 4to. 460 pp. Paper. $2.50. Hoelling, Joseph N. Untersuchungen iiber die Bewegung des Planeten (13) Egeria. Kiel: Astronomische Ahband- lungen. No. 12. 1907^ 4to. 30 pp. Paper. Jost, E. Untersuchungen iiber die Parallaxen von 29 Fix- sternen. Karlsruhe: Veroffentlichungen der Grossher- zoglichen Sternwarte zu Heidelberg. (Astronomisches Institut.) Band IV. 1906. 4to. 171 pp. Paper. Pickering, W. H. Lunar and Hawaiian physical features compared. 4to. 28 pp. 16 plates. Qoth. Saint- Blan cat, D. Action dune masse intermercurielle sur la longitude de la lune. Paris: Gauthier-Villars. 1907. 4to. 103 pp. Paper. Sp:ares, F. H. Announcement of preliminary results for vari- able stars. Columbia: University of Missouri. (Laws Observatory Bulletin, No. 10.) 4to. 22 pp. Smith, C. Michie. Widened lines in sun-spot spectra. Ko- daikanal Observatory: Bulletin No. VIII. 4to. 20 pp. Paper. Astronomical Society of the Pacific. 177 Stein, J. W. J. A. Beobachtungen zur Bestimmung der Brei- tenvariation in Leiden. Haag: Annalen der Sternwarte in Leiden, Neunter Band, Heft L 1906. 4to. 237 pp. Paper. Conference astrophotographique intemationale de Juillet 1900. Circulaire No. 12. Paris: Gauthier-Villars. 1907. 4to. (Ill) + f 14) + (A127) + (B152) pp. Paper. Report of the British Association for the Advancement of Science, 1906, York. I^ndon: John Murray. 1907. 8vo. cxxiv + 831+89 pp. Qoth. 17H FubJicaUans of the Astronomical Hoctety, OFFICERS OF THE SOaETY. Mr. Chab. S. Cusninc / Mr. A. H, Baicock Fira Vicc-PrtsidtM Mr. W. W. C*«».ELL Stcani Vwf-Prtsidtml Mt. Geo E. Hale Third yicr-PreaJenl Mr. R. T. CKAWrons (StudenU' OhKrvatar7. Berkeley) Stcrttary Mr, F. R. Ziu. TrttHrtT Beard of Dtrrclort — Ueuci. Aitkek. Samcixk. Bducksaltii, Campiell. Cbockeb. Finaiiei Commilte* — -McMri. RicHa>[>son, Ciiocmi, Buickhalthi. Library Commiltn — Meura, CKAWfatb, Ikvihc, Towhuv. Cammitttt en tkt Cemtl-Midal — Hesf^n. Cami-ecll (ex-omcloi. nvnciBALTu. PmilNK. The BItention of new mtmben is called to Article VIII of Ibc Bt-Uwc, obich ptovidei thai tbe annual lubicriptioii. paid oa electioD, covera Ihe calendar rear ODly. SubaequCDl annual paymenU are due on January iil of eacta succeedini- calendar year. Thil rule i> ncceuaiy in order to make our booklceepin^ as simple u passible. Duea sent by mail ihould be directed la Aitranomical Soqiely of [be PaciGc. B06 Franklin Street, San Francisco. It is intended that each member oi the Society ahall receive a copy oC each one of the Fublicationa for Ihe year in which be was elected to membenhip and (or ■II nibsequcnt years. If there have been (unfarCunately) any amisBions in this matter, it is requested Ibai the Secretaries be at once DOIi£ed, in order ihal the _:..z 1 J, )^ supjilied. Member* are reqneiled to preierre the copies of Ihe blnd*"fi of (he of tt will also Once Complet; will member within the United Slates can obtain books from the Society's library by sending his library card with ten cents in stamps lo the Secretary A- S. P.. Students- Observatory, Berkeley, Cal., who will return the book and the card. are printed in the Fublitaiinm is decided simply by convenience. In a pneral way. those papers are printed first which are earliest accepted for nublication. Papers intended to be printed in a given nnmber of the Pnblicalioui ehauld be in Ihe hands of the Committee not later than Ihe aoth of Ihe month precedug date of publication. It is not possible to send proof sheets of papers 10 be printed to ■ulEora whose residence is not within the llniled Stales. The responsibility for Iba views eipressed in the papera primed, and for Ihe fonn ol their expression, rent The titld of' papers (or reading should be communicated to either of the Sec retsriea as esrly a* poesible, aa well as any changes in addresses. The Secretary in San Francisco will tend 10 any member of Ihe Society suilablt slutioneiy. itamped with the seal of the Society, at cost price, u foUowa: a block of letter ._. _. pj^,, ^ package of e— -' — '^'- — "-^ 19. The Kndingt a I.US". '.order or in U. S. postage at Mount Hamilton during I Aslronomical Society ol PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XIX. San Francisco, California, August 10, 1907. No. 115, OUR DEBT TO ASTRONOMY: By Russell Tracy Crawford. Astronomers are so often asked questions such as **What is astronomy good for?" **Why waste your time and energy upon anything so immaterial and unpractical as astronomy?'' **What good does it do to know where a comet is going?" etc., that it seems opportune and fitting to answer such questions quite thoroughly. For this reason the subject "Our Debt to Astron- omy" has been chosen for this address. These questions and many others of a similar nature show how little thought is given by the general public to such matters, and how carried away they are with the intensely practical ideas of this rapidly advancing age, which seems to have emblazoned upon its ban- ner not "Excelsior," but a glaring monogram of the United States with the curve at the bottom of the U eliminated from the picture. Among other things 1 hope to convince the followers of this banner of the almighty dollar that astronomy is one of its most potent aids and should therefore be one of its pets, worthy of its support. Upon this subject Professor Young writes as follows in the introduction to his **General Astronomy": — **At present the end. and object of astronomical study is chiefly knowledge pure and simple; so far as now appears, its development has less direct bearing upon material interests of mankind than that of any other of the natural sciences. Tt is not likely that great inventions and new arts will grow out of its laws and principles, such as are continually arising from physical, chemical, and biological discoveries, though of course it would be rash to say that such outgrowths are impossible. But the student of astronomy must expect his chief profit to be intellectual, in the widening of the range of thought and con- ception, in the pleasure attending the discovery of simple law working out the niost complicated results, in the deHght over the beauty and order revealed by the telescope in systems otherwise invisible, in the 1 82 Publications of the recognition of the essential unity of the material universe, and of the kinship between his own mind and the infinite Reason that formed all things and is immanent in them. . . . "At the same time it should be said at once that, even from the lowest point of view, astronomy is far from a useless science. The art of navigation depends for its very possibility upon astronomical prediction. Take away from mankind their almanacs, sextants, and chronometers, and commerce by sea would practically stop. The sci- ence also has important applications in the survey of extended regions of the country, and the establishment of boundaries, to say nothing of the accurate determination of time and the arrangement of the calendar." It is the intention here to go further than this, and to speak not only of the present, as Professor Young does, but to go back to the beginning of things and to show the principal accounts in "Our Debt to Astronomy." Let it be known at the outset that for many centuries, from the beginning of terrestrial affairs, the history of the world is practically the history of astronomy. For many centuries, we cannot say just how many, astronomy was the one and only agent to quicken the thoughts of men and to lead them to a comparatively high state of intellectual development. Place ourselves, if we can, in imagination back into the so-called pre- historic times, and it will at once be evident that the most striking phenomenon of nature — viz., the rising of the Sun, Moon, and stars in the east, their daily journeys across the sky, and their setting in the west — would be the first thing to draw thought and set active minds to speculate. Once started, the keen mind would soon find other phenomena of astronomy to work upon, and in this way was built up that foundation for tlic superstructure of culture and knowledge which we find in the possession of earliest historical man — our first debt to astronomy. We find that, in the beginning of what we may call authentic history, astronomy was purely a practical science. Theoretical astronomy there was, wild as it may have been, but it was the practical side of astronomy that was most developed and cultivated. It was very necessary in those times, when agri- culture was the main industry, to know when to sow the crops, and when to reap them, — in other words, a knowledge of the season was essential to existence itself. And how, indeed, was a knowledge of the seasons to be had, not only then but now, exce|)t by a careful study of the wanderings of the Sim from Astronomical Society of the Pacific. 183 its southernmost position to its most northern station, and back again, during the course of the interval of time that we call a year? Let us consider, in particular, the case of the Egyp- tians. Egyptian civilization would have been impossible but for the Nile floods, which appear with great regularity. The rising waters reach the region of Heliopolis and Memphis almost exactly upon the day that the Sun is at the summer solstice. It is very evident, then, that the Egyptians before us were under obligations to the astronomers of their age to inform them of the time when the Sun would be at the sum- mer solstice. It is no wonder, then, that the Egyptians com- missioned their astronomer-priests to observe carefully for the helical rising of Sofhis or, as we now call it, Sirius, the dog- star, to give them the necessary datum upon which their year's material prosperity depended. As every advance in early knowledge and civilization was an essential stepping-stone to our present acropolis of culture, we of to-day owe this a second debt to astronomy. It must ever be borne in mind that our present-day knowl- edge has not been attained by the spontaneous outburst of genius in a single generation, but has been built up slowly, step by step, from earliest times, each single advance being a necessary precursor of later development. Hipparchus must precede Ptolemy, and Ptolemy must precede Copernicus. Copernicus made the way easier for Kepler, and Kepler in turn added the stone upon which Newton built, and so on. To every contributor of a stone in our Temple of Knowledge, whether it be in foundation or superstructure, we of to-day owe a debt. Incidentally, we have a decided personal interest in the theoretical astronomy of the Babylonians, who gave us the week of seven days, with the names taken from the Sun, Moon, and the then-known five planets, Mercury, Venus, Mars, Jupi- ter, and Saturn. Had Uranus and Neptune been known to them, our week would have been nine days long instead of seven, with one day in nine for rest. To astronomers and their science we owe the evolution of the ideas and conceptions of the size and shape of our globe. The earliest peoples believed the evidence of the senses, and thought that they lived upon a large flat surface. More ad- 184 Publications of the vancecl ideas were that the Earth was a truncated cone, and then a cylinder, and finally, even so early as the time of Pythagoras, it was shown to be a sphere. As to its size no definite conception was had until comparatively recent times. The determination of its dimensions to-day would be impos- sible but for the astronomer. Astronomy has not always advanced, but has had its set- backs, from which, however, it has nobly recovered. This brings me to speak of the retarding influence of Aristotle and Ptolemy upon the world's knowledge and culture; its overthrow brought about by astronomers, and the wonderful results therefrom — one of the greatest of our debts to astronomy. In the third century B. C. Aristarchus of Samos and others of less note had asserted that the Earth was in motion — a very advanced idea for the time ; but they could not prove it. Then came a backward step, taken by Ptolemy, who ap- parently proved that the Earth was not in motion, but was immovable at the center of the universe. This idea held sway for fourteen centuries, until the time of Copernicus. Its overthrow came at about the time of the downfall of the influence of Aristotle. These two accomplishments were the most vital forces of the Revival of Learning. It has well been said that Aristotle retarded the progress of the world's knowledge and culture more than any other one man. His dictum was the undisputed law in the realms of knowledge for seventeen centuries. If any one dared to present an idea contrary to Aristotle the sneering question was ever ready » "Do you think you know more than Aristotle?'' and the investigator was completely squelched. This absolute servility to the dogma laid down by the great philosopher furnishes one of the most remarkable pictures in history. But sooner or later this had to end^ and the end came with G.\lileo, the astronomer. I may recount here the beginning of this end. Aristotle had said that a large heavy body would fall from a given height in less time than a small light one. For seven- teen centuries it had never occurred to any one to investigate experimentally the truth of this assertion, or else no one had dared to try it. Galileo, the astronomer, however, was not content to take the word of anybody, even Aristotle, upon a matter which could be proved or disproved so easily as this. Astronomical Society of the Pacific. 185 one. Dramatic indeed must have been the scene when the great astronomer mounted to the top of the leaning tower of Pisa and let fall simultaneously a large heavy body and a small light one, and great indeed must have been the aston- ishment of the populace gathered to witness the experiment when they beheld the two bodies falling side by side and reaching the Earth at practically the same time, demonstrating, as Kipling puts it, that **heart-breaking power, the perversity of inanimate things.'* At that instant fell also the influence of Aristotle in the scientific world. Copernicus had just previously shown that the Earth is in •motion about the Sun, and when Galileo clinched this idea, so to speak, by turning his telescope upon Jupiter and there beholding the four moons revolving about the central mass, a miniature world, the revolution was complete. It is difficult lor us to imagine what a convulsion must have taken place in the minds of men at that time. The Church had taught that the Earth was stationary, and even to think anything else was the greatest heresy, as it was contrary to Holy Writ. In view of this, is it any wonder that we had the Dark Ages? Because of the unswerving adhesion to dogma in those days it is, again, no wonder that the great astronomer, Galileo, was brought before the Inquisition, tried and convicted of heresy, furnishing one of the most dramatic, almost tragic, incidents in the history of science. But the ideas once started by Copernicus and Galileo soon began to spread and found firm supporters, and the world once more started on the way of progress. We cannot begin to appreciate the effects of such a revolution in the world's thought. At first sight one would say, "What a loss of importance and dignity!'' We are no longer the great It, — the center of the universe about which all else must turn, and to which all else must be subservient. But, on second thought, we would say, and do now say, "What a gain in beauty and grandeur!'' We now find ourselves whirling about the great Sun in the infinite sea of ether, gaz- ing into its immeasurable expanse. Can any one estimate the amount of dollars and cents in this debt we owe to astronomy? No; it is above dollars and cents. Following quickly upon the steps of these two great astron- omers we have Kepler, who gave us his laws of planetary motion, by means of one of which the scientific mind was 1 86 Publications of the freed from the so-called perfect path, the circle, and was introduced to the use of the general conic. His work, in turn, formed the stone upon which Sir Isaac Newton built so well. It would be a long story, indeed, to recount the various debts we owe to this man, our greatest astronomer. For the more practical-minded, however, I will call attention merely to one of his accomplishments. In evolving his universal law of gravitation, and in furtherance of his astronomical investiga- tions, ^it became necessary for him to invent a new branch of mathematics — namely. Calculus. Is there any one so daring as to estimate the commercial value of calculus? The idea is staggering. It is beyond human power to make the com* putation. Without this powerful implement, due to astron- omy, what could be done in applied mechanics? Where would our sky-scrapers be? How could we build our battle- ships? Where would our electric-cars be? How could our enormous bridges be built? — and so on, almost ad infinitufn. Less than a month ago, while coming in from Oakland on the electric-car, a friend asked me the old question, in rather inelegant English, "What is astronomy good for?'* Among other things I said, **I suppose you see no connection between astronomy and this electric-car?" The answer was a ready **No!" The connecting-link is this same calculus. We find, not only in the applied sciences, but also in many of the natural sciences, higher mathematics to be an absolute necessity. And to what are the higher branches of mathe- matics due? The answer is, "Principally to astronomy." I wish to quote here from Dr. William F. White's article on **The Nature of Mathematical Reasoning,'' in No. 609 of "The Open Court." He says, ** Behind the artisan is a chemist, behind the chemist a physicist, behind the physicist a mathe- matician." There he stops, but I now add, behind the mathe- matician the astronomer. Another great debt that we owe to astronomy is one on behalf of our peace of mind. I^>om the beginning up to the present time there have been, and now are, many people filled with superstition concerning the heavenly bodies. Thanks to astronomy, these are becoming fewer and fewer. In ancient times whole nations were thrown into a panic by an eclipse of the Sun ; armies on the eve of battle were commanded to halt, with disastrous results, to await the passing of the ill- Astronomical Society of the Pacific. 187 omen of an eclipse of the Moon. Comets were supposed to be within our own atmosphere, and to bring pestilence and dis- ease. These phenomena have been shown by astronomers to be ordinary affairs in the celestial mechanism, having no bearing upon our regular existence. Unusual conjunctions of several planets are even now by some thought to have an important bearing upon the affairs of life. Many crafty people to-day make a livelihood by imposing upon the more supersti- tious and easily-fooled people by casting horoscopes. One of our daily papers thinks so little of the value of its space as to give up a quarter of a column in every issue to the publication of Cozette's horoscope for the next day. Within the last few weeks the papers announced that a comet had been discovered by an astronomer on Mt. i^tna, which was coming directly toward us and would soon annihi- late the Earth. Immediately after the appearance of this wonderful announcement this observatory had many letters of inquiry concerning it. Some people evidently believed in it, and wanted to know the exact date when the direful catastro- phe would occur. Probably there will always be some who will be thus taken in, but, thanks to the teachings of astronomy, we live in practically perfect peace of mind regarding these things. Nations are no longer convulsed by an unexpected eclipse, and astronomers royal are not decapitated for failure to predict them. A study of the simple elements of astronomy would be very beneficial to artists and writers. They often make serious mistakes through mere ignorance. It is not very uncommon to see an otherwise beautiful painting spoiled completely by a delicate crescent Moon with its horns pointing toward the Sun. A note in No. 383 of the Observatory calls attention to the fact that in chapter I of **J^"^ Eyre," by Charlotte Bronte, occurs this expression: "(The Moon's) newly risen crescent, attesting the hour of eventide/* a statement which makes the author appear ridiculous. Many instances. of this kind could be cited. Finally we come back to Professor Young's statement, to consider the present-day, all-absorbing, doUars-and-cents value of astronomy. You have all probably traveled at night, resting more or less comfortably in a berth of a Pullman attached to an express train, which in its course thunders by a freight 1 88 Publications of the train on a siding. You give but little, if any, thought to it, having confidence in the men running the train. These men in turn have confidence in their nmning because they are run- ning "on time." Think what it means to the railroads of the country, and to the public, to have the trains running "on. time." To be able to handle the enormous traffic of to-day correct time is an absolute necessity. Where do the railroads get their correct time? Another account in our debt to as- tronomy. Again, when it became necessary to run the boundary-line between Canada and the United States astronomers had to be employed. Our maps cannot be made without a knowledge of practical astronomy. Extended surveys also require a knowledge of practical astronomy. I will call attention to one more, perhaps the greatest, com- mercial debt we owe to astronomy; that is, the service it renders to navigation. Were it not for the data furnished by astronomers, commerce by sea would practically stop. The sailing-master on the high seas could not determine his posi- tion, nor in what direction to head his ship in order to reach a desired harbor. Think what this means in dollars and cents, and estimate it if you can. For this one service alone the science of astronomy is worth more in dollars and cents to the world in one week than has been expended upon it since the beginning of civilization. Do you think that Great Britain, for instance, would take in exchange an amount equal to its national debt for what astronomy gives her? I answer for you, most emphatically, "No." Even these commercial values sink into insignificance when we consider again, in general, what astronomy has done for us in giving us the laws upon which mechanics is based; in pushing mathematics to its present state of development, the effect of which ramifies rapidly ; in being one of the most powerful factors in bringing us to a better understanding of nature; and in broadening our views and taking, us out of the narrow confines of a little plain, immediately surrounding the .^gean Sea, and launching us into the infinite realms of space. In conclusion, I wish to answer one more question — namely, "While sonic parts of astronomy may be of value, why exert so much thought and energy upon other parts which are purely ^hstrsict and theoretical?" The answer to this is that Astronomical Society of the Pacific. 189 we never can tell to what such abstract speculations may lead, and that, in the end, they may give us something exceedingly valuable, either in the commercial world or in the realms of culture and knowledge. A comparison with prospecting may make it clearer. The miner digs day after day with apparently no return. He may continue to do so with no result, no matter how long he labors ; but, on the other hand, at any moment he may unearth a rich vein which will more than repay him for his efforts. So it was with Kepler, when he dug through Tycho's observations day after day with no result, until finally, after much labor and the use of an enormous store of patience, he struck the vein of planetary motion, and his wonderful laws were brought to light. It was Michael Faraday who said so well, **There is nothing so prolific in utilities as ab- stractions." And now, in closing, T desire to express the hope that you who have heard what I have had to say, and those who may hereafter read what I have said, will ever feel it unnecessary to ask in inelegant English, "What is astronomy good for?" Berkeley Astronomical Department, July 13, 1907. THE LOST RINGS OF SATURN. By Arthur B. Turner. The Moon long since became a dead world, without air or water. The planet upon which we dwell is well advanced in its development; its surface has cooled and hardened, but it still has air and water, the great life-giving elements. We look out upon the planet Mars with its surface covered by canals in the struggle of the inhabitants to get water to supply their needs. But beyond Mars, at a distance more than nine times our distance from the Sun, there circles a world, re- splendent in the making, surrounded by satellites and rings, and taking over twenty-nine years to make its majestic swing around the Sun. This orbit formed the boundary to the solar system down to the discovery of Uranus, by Herschel, in 1781. Saturn has a diameter a little more than nine times that of the Earth, and makes over two revolutions on its axis in one of our days. The result of such swift rotation is lo tw^Ve the planet appear perceptibly flattened at the poles when viewed in the telescope. A vast envelope of clouds surrounds the fiery ball, which is light enough to float on water.' ^^H L SATELLITES AND RINC5. ^^H Ten moons swing around this globe, obedient to its attrac- tion, the last one having been discovered by Professor W- H. PicKERiMG, of Harvard. The ninth satellite— PA irfri'^s remarkable in the fact that it disobeys the ordinary laws of solar motion by moving backwards around the planet. But the most remarkable feature of this world— distinctive from all other celestial bodies — is the wonderful system of rings, first discovered by Galileo, and which appeared to him as bright stars on either side of the disk. He says of his discovery: "Looking on Saturn within these few days I found it solitary without the assistance of its accustomed stars, and in short perfectly round-^are perhaps the two smaller stars consumed like spots on the Sun: have they suddenly vanished and fled? Or has Saturn devoured his children?" And so this old pioneer of astronomy diet! without realizing that what he had discovered was one of the greatest anomalies of the Astronomical Society of the Pacific. 191 solar system. It was left for Huyghens, in 1655, to announce their true character. There are three wide, thin rings surrounding the planet in the plane of its equator, and ranging from eleven thousand to eighteen thousand miles in width and about fifty miles thick. They are inclined to our path around the Sun, so that we see them at various angles as they reflect back to us the Sun's rays. It was thought at one time that they consisted of fluid or solid, but the mathematicians proved that such rings would soon fall lo pieces, and that probably they consisted of swarms of particles like meteors, each particle following an independent path around Saturfi, just as the Moon does around the Earth. By spectroscopic observations of the rings by the late Pro- fessor Keeler, it was shown that they must consist of discrete particles. THE LOST RINGS. The plane of these rings moves parallel to itself as they accompany the planet around the Sun, so that about every fifteen years this plane will pass through the Sun. The Earth in passing around the Sun will view the rings in varying positions. This year the plane of the rings passes through the Sun, and from April 12th to July 22d we face the unil- lumined side of the rings — the .Sun being north and the Earth south of their plane. To us, then, the rings will appear as a black bar crossing the disk of the planet, with possibly a faint line of light where the rings extend on either side of the ball. In 1 89 1 the great Lick telescope failed to show any trace of the rings when in a similar position. From July 22d to Octo- ber 4th the rings reappear as a narrow line of light on the two sides of the planet, as shown in the figure above. From October 4 to January 6, 1908, the Earth will be north of the plane of the rings and the Sun south of this plane, and the above phenomena will be repeated. It was this disappearing of the rings that so puzzled Galileo. When the rings are more favorably situated we can see the shadow cast on them by the planet, and also the disk shining through the inner dusky "crepe" ring. College of the City of New York, Department of Mathematics and Astronomy. 192 Publications of the PLANETARY PHENOMENA FOR SEPTEMBER AND OCTOBER, 1907. By Malcolm McNeill. PHASES OF THE MOON, PACIFIC TIME New Moon Sept. 7, 1^ 4m p.m. First Quarter.. *' 14, 7 40 p.m. Full Moon " 21, I 34 P.M. Last Quarter.. " 29, 3 37 a.m. New Moon Oct. 7, 2^2i^A.yi. First Quarter.. " 14, 2 2 a.m. Full Moon " 21, I 16 A.M. Last Quarter. . . " 28,11 51 p.m. The autumnal equinox, the time when the Sun crosses the equator from north to south, is September 23d, 9 p.m., Pacific time. Mercury is a morning star on September ist, rising about half an hour before sunrise, too near the Sun for naked-eye observation. It is moving toward the Sun, and passes superior conjunction on September 6th, becoming an evening star. It then moves out toward greatest east elongation, which it reaches on October 23d ; but as its motion carries it southward relative to the Sun, the conditions for visibility are poor, and it does not remain above the horizon as much as an hour after sunset at any time during the period. While it is still a mom- ine; star on September 3d, it is in very close conjunction with Venus, passing to the north of that planet 26', less than the apparent diameter of the Sun, but both bodies are too near the Sun to be seen. J^enus, like Mercury, is a morning star on September ist, too near the Sun to be seen, and passes superior conjunction, becoming an evening star on September 14th. After this date its motion relative to the Sun is eastward, and by the end of October its distance is about 12° ; but it is also moving some- what southward, and on October 31st it sets only a little more than half an hour after sunset, so that it is scarcely possible to make any naked-eye observations during the two months. This is rather a rare occurrence. ^[ars is still in fine position for observation, setting about half an hour after midnight on September 1st, and shortly after 11 r.M. on October 31st. It has begun to move rapidly eastward, and during the two months* period moves 33° east- ward and 8° northward from a position among the stars of the niilk-di])per group in Sa^i!;ittar{us to the middle of Capri- Astronomical Society of the Pacific, 193 corn. On September 2cl it is a little more than 1° south of oSagittarii, the right-hand star in the bottom of the bowl of the dipper, and on September loth passes less than 1° north of TSagiitarii, the left-hand star in the bottom of the bowl. It is in perihelion on the morning of September 26th. Its distance from the Earth changes from fifty millions of miles on September ist to sixty-six millions on October ist, and eighty-five millions at the end of the month. By September 1st its brightness is about forty per cent less than it was at its maximum, in early July, and it begins to fall off rapidly during the two months, so that at the end of October it is only one fifth as bright as it was at opposition, but it will still be bright enough to be conspicuous. Jupiter is a morning star, rising about 2^ 30™ a.m. on Sep- tember 1st, at about i a.m. on October ist, and at a little before 11** 30" p.m. on October 31st. It is in the constellation Cancer, and moves about 9° eastward and 2° southward during the two months. On the morning of September 3d it makes a very close approach to the Moon, and for some places will be occulted. Saturn is in fine position for observation throughout the months of September and October. On September ist it rises about an hour after sunset, and comes to opposition on Sep- tember 17th. On October ist it does not set until nearly 5 a.m., and on October 31st it sets at about 2^ 30™ a.m. It is in the western part of the constellation Pisces, and moves about 4° westward and 2° southward. The phenomena of the rings are still very interesting. On September ist both the Sun and Earth are below the plane of the rings, and we are therefore looking at the illuminated face. The rings appear very narrow, and continually grow narrower until about October 4th ; at this date the Earth passes through the plane and we see the rings edgewise. It will take a good telescope to show any- thing of the rings in such circumstances. For the remainder of the year after October 4th the Sun and Earth are on oppo- site sides of the plane, and therefore the side facing us is the dark side. The rings widen out a little until about the end of November, and a fine telescope may show this by the curva- ture of the thin line of light reflected from the edge. Uranus is in fair position for observation in the evening sky. On September ist it sets at about 12^ 30"* a.m., on 194 Publications of the Astronomical Society, &c. October ist at about lo** 30™ p.m., and on October 31st at about 8^ 30" P.M. Its motion among the stars is very small — a little westward until Septeml)er i8th, and then about I** eastward by the end of October. It remains in the constella- tion Sagittarius, north of the milk-dipper group, about 3** north of and a Sagittarii, the stars in the bowl nearest the handle. Neptune rises shortly after i a.m. on September ist, and shortly after 9 p.m. on October 31st. It is nearly stationary in Gemini. NOTES FROM PACIFIC COAST OnSERVATORIES. Note on Comet d 1907 (Daniel). This comet was discovered by Daniel at Princeton on June 9, 1907. The preliminary elements by Crawford, Ei.varson, and Miss Gl.\ncev. of the Berkeley Astronomical Depart- ment, indicate that it will pass peiihelion on September 4th at about half the Earth's mean distance from the Sun. In the early part of July 1 observed the comet here with the iz-inch telescope, and fonnd it to be of about the sevenih magnitude and growing brighter. Photographic observations with the Crocker photographic telescope were begun on July 10th and continued every night until July 21st, after which the late setting of the Moon prevented exposures of sufficient length to be valuable. With the Moon away it was possible to obtain exposures two hours long. The first photograph showed a tail of five or six degrees' length with two longitudinal dark lanes and several knotty condensations. The second, (July nth) also showed con- densations, but since the date of this photograph the tail has consisted of straight or slightly curved, .smooth streamers. No identity could be established between the condensation of the tail of July loth and those of July nth, and therefore their velocity of recession from the nucleus could not be determined. Since the photographs were begun the comet has grown rapidly brighter, and the tail has increased rapidly in length and complexity. On the night of July 20th no less than six streamers diverged from the nucleus, and these subdivided into several branches, extending about 12° from the head. In photographic observations of comets it has been found that, as a rule, the tail changes completely between consecutive nights, so that it is desirable that negatives be made at intervals of a few hours in order that the velocity of particles within the tail may be determined. With this object in view, a second lens, of 6-inch aperture and 32-inch focal length, was mounted 196 Publications of the beside the Willard lens. By this means it is possible to obtain two one-hour exposures each night, together with one two-hour exposure, which will show more of the faint detail. The appa- ratus was used in this way on the nights of July 19th and 20th. Measures made on the point of forking of the principal tail on the short-exposure plates of July 20th indicate a component of velocity of recession from the head, perpendicular to the line of sight, of about seventy miles per second. This apparent motion of the point of forking may be real, or it may be an illusion due to the closing together of the two branches of the fork, which would cause the point of separation to seem to move outward. The comet is now of the third magnitude, and is rapidly growing brighter. Since July 17th the tail, as well as the nucleus, has been visible to the eye. An ephemeris computed from Crawford's elements shows that the comet will reach its maximum theoretical brilliancy about August 20th, when it will be about twenty times as bright as on June 15th and about twice as bright as it is now. This calculation is of course based on the assumption that all of its light is reflected sun-light, and the actual brilliancy may much exceed the theoretical. At the time of perihelion the comet will be about an hour and a half west of the Sun in right ascension, and it is hojjed to extend the series of photographs much further. Lick Observatory, July 24, 1907. J- ^« JJUNCAN. Spectrograph ic Observations of Venus for Solar Parallax. The determination of the solar parallax by spectrographic methods has long been under consideration among astrophysi- cists, but until very recently it has been thought to be out of the reach of spectrographs now in use. The work of taking a series of spectrograms of stars having small latitude was begun by Sir David Gill at the Cape Observatory, and is now in progress. The accuracy with which this series will deter- mine the solar parallax has not yet been fully ascertained ; at least it has not been published. Professor Kustner, in an article reviewed by Dr. J. H. Moore in Vol. 17, 197, of these Publications, gets a p. c. of ±: 0.22^"^ for a single plate of A returns: using eighteen plates, he obtained the value 8".844 ±: o".oi7 for the parallax. Astronomical Society of the Pacific. 197 The measures of check-plates of Venus, taken with the remounted Mills spectrograph in 1904 and 1905, agreed well enough to warrant the taking of a few plates at each of two successive elongations of the planet, to see what weight a value of the solar parallax would have if detennined spectro- graphically from Venus alone, and to find out what increase of power would be necessary to put this method on a par with the most accurate of those now in use. The elements of the orbits of the Earth and the other planets are well determined, but the dimensions are relative. If at any time we can determine the absolute distance from the Earth to another planet, or measure the velocity of any planet with respect to the Earth the absolute size of the whole system can be readily found. Knowing the size of the orbit of Venus relative to that of the Earth, the velocity of light and a few absolute wave-lengths we can determine the solar parallax by spectrographic observations of the planet. While the velocity of Venus with respect to the Earth is not so great as that of the Earth with reference to a star on the ecliptic, and while the large hour angles necessary in taking spectrograms of Venus are inconvenient, if not prejudicial, the brightness of the planet and freedom from unknown changes in velocity due to satellites and from small spectral variations such as may be encountered in stars, will more than counter- balance the disadvantages when we come to use a more power- ful apparatus, such as we are about to discuss. The spectro- graphic method in general is relatively unaffected by the things that are troublesome in other methods, the most important of which is refraction, and perhaps least important, on account of its accurate determination, the size of the Earth. This method must assume Doppler's principle. The measurements of the two series of plates taken at the last two elongations of Venus showed greater discrepancies than had been expected, and the mean of the two sets differed by 0.4*™, so an investigation of the cause for the difference was undertaken. It came out that sky-plates taken with the instru- ment in the same adjustment as was used for the later series differed from the computed values by the same amount as did the Venus-plates, leading to the conclusion that slight differ- ences in the closure of the slit, or a dust grain, may affect the velocity of a plate by interfering with the symmetry of the 198 Publications of the L comparison-lines. The value obtained for the probable error cf a single Venus-plate was ± 0.23'"". of a single sky-plate :+: 0.18'". From this we may infer that an instniment five times as ixjwerful would give a result five times as accurate, or :i p. c. of ± 0.04*™ for a single plate, that is +: 0.006''" for Ihe mean of fifty plates. This would be about the accuracy of an Eros detenu in at ion of the parallax ± o".oo4. A grating ruled 15,000 lines to the inch would give, in the third order, the same angular dispersion as the Mills at A 4500; 20,000 lines to the inch, third order, or 15.000 lines, fourth order, would give a third more angular dispersion than the Mills, and the resolving power in cither case would be over five times that of the Mills if it were a 6-inch grating. The focal length of the Mills camera would have to be multiplied by 3.5 to give sufficient linear dispersion, but it might not pay to increase the collimator focal length in the same ratio, owing to Ihe limited size of gratings that can be ruled. Supposing that this spectrograph and the horizontal telescope necessary to concen- trate the light on the slit effectively utilized twenty per cent as much light as the Mills attached to the Lick 36-inch tele- scope. Throughout the rest of the optical train, the grating would have to throw eight per cent of the incident light into one of the higher orders on one side — not an entirely unknown occurrence —in order to photograph the spectrum of Venus in thirty minutes. The Mills gives a hysical Jour- O. nal, XIII, 90, 1901 T, Aquilv hours, and the observer can easily make certain that the stars which lie selects are those most urgently in need of measurement. The catalogue in printed form comprises two quarto volumes of more than one thousandpages. but. in spiteof its size, it is a marve! of compactness. The introduction, which might easily have been expanded into a hundred pages or more, is condensed into very slightly more than eight ; the index to seven thousand pairs discovered by the more prominent modern observers is reduced by an ingenious scheme of tabulation to but ten pages, and the seven tables giving the classification when possible of the more than thirteen thousand pairs, as to the character of their motion, requires but eight pages more. This ditTicult principle of securing the utmost conciseness has been followed throughout, yet it does not appear that a single fact of impor- tance has been omitted. The first volume contains descriptions of the 13.665 double stars which have so far been discovered within 121° of the north pole. Through an appendix even the most recent dis- coveries of HusSEY and Aitken are included, so that every double star whose discovery was published not later than 1906 will be found in this work. The southern limit of — 31° which is adopted for the catalogue includes all of the stars which can be well observed at the northern observatories. In Mr. Bl'RNHam'k opinion it will probably not be until the end of the present century that measures and discoveries of pairs further south will have so accumulated as to make a similar catalogue of the southern heavens desirable. The vexed question. Which of the pairs recorded by various astronomers as double shall be included in the catalogue? is here solved by retaining all of them. Mr. Burnuam wtAcs, oi\ this subject: — "The qiicstioii of drawing some kind of arhilrary line between what might he presumed lo be physical systems, and those which it was practically certain could not belong lo that class, was considered at an early day in the preparation of this work. It was soon apparent, from a practical application of the principles which were supposed lo govern a judicious separation of the material into these two classes, that il could not be successfully done, A too liberal application of the rule would reject a comparatively small number and so accomplish but little in reducing the size of the catalogue; while, on the other hand. ihe rigid enforcement would necessarily exclude many stars which are of some interest at le.ist, in consequence of changes already shown from proper motion. Then again, the names of ihe great astronomers attached to these stars entitle them to a place in the first catalogue of double stars, independent of any consideration of the stars themselves. I have therefore included them all, and as far as possible remeasurcd the large number of neglected pairs of the old obsen-ers for this work," It seems to us that this is a most fortunate decision. It is to be noticed that, with very few exceptions, it is only the briglit or very close doubles which have thus far been observed, and that the orbits of such pairs only arc known to us. How many faint and comparatively wide pairs there are which art true binaries we cannot conjecture. There is at least one such example (Krueger 6o). of which the components are of th/ 9.0 and 12.0 magnitude and 3".5 apart, whose period will almost certainly not exceed two hundred years. If two thou- sand or three thousand such pairs are catalogued and a con- siderable number of these afterward found to be binary, this will go far toward solving the general question of the com- parative masses and distances of the faint and bright stars. Mr. Bt'HNHAM finds that 585 pairs have a common pri^pcr motion. Many of these are faint and widely separated, ami yet it is very probable that they are physically connected, the periods being reckoned in thousands of years. Perhaps the two best-known examples are fi' Herntlis and 40 Eridaiii. the former being separated by 30" and the latter by So". Thai these great distances could have been attained through tidal action seems hardly possible; wc cannot even conjecture what the form of their relative paths is likely to be. but to secure and record at least one good measure on every such pair is a debt which the astronomers of to-day owe to posterity. Per- haps the most liberal scheme for the exclusion of double stars is that employed by Isngs in his Reference Cata- logue of Southcm Double Stars. Vet, were this rigorously applied, not only would the distant companions of fx Hercutis Astronomical Society of the Pacific. 221 and 40 Eridani be rejected as of no interest, but these two attendants, each of which is a faint binary of comparatively short period, would both be excluded also. The first volume contains the position of each star reduced to 1880.0, and the date, position-angle, distance, and magni- tudes at the time of the first measure. For fully ninety per cent the identification is given ; many of those in which this is omitted are too faint to be found in any of the catalogues. The second volume gives a sufficient number of selected measures to show the character of motion in each pair, and in addition to these the complete references in each case to every measure which has ever been made on it and to all important notes and papers relating to it. The latest values of the proper motions of the principal stars are also included. Mr. Burn- ham is decidedly of the opinion that when many good measures are available the more uncertain ones should be unhesitatingly rejected. He says on this point: — *'For obvious reasons only the best measures by the best observers are selected as a rule, and those made on a single night have been generally rejected, except when there was nothing else in point of time to take their places. It must be clear to every one that the omission of all indifferent and superfluous observations necessarily adds to the value and usefulness of this work. The author has not been handi- capped or limited in any way as to space to be used ; and in the citation of observations and in the comments relating thereto he has omitted nothing that in his judgment would be worth giving. It goes without saying that a large number of the published measures of double stars should be rejected in any investigation or discussion as to the relative motion of the components. There need be no difficulty or hesitation in deciding as to the proper material to be used. If all the observations — good, bad, and indifferent — are employed in the computation of an orbit, it is certain that the value of the result will be correspondingly impaired, and no method of treating the doubtful material will prevent this." Beside this enormous labor of compilation there is a con- densed but most thorough discussion of each pair in which there has been change. Hundreds of new and carefully con- structed diagrams are given in this connection. Certainly no work could be more valuable or more authoritative than this. It is needless to say that Mr. Burnham never attempts to get out of the measures more than the material will certainly show. Even in the introduction space is spared to emphasize the inutility of attempting to compute orbits when the measures 222 Publications of the Astronomical Society, &c. are wholly insufficient for this purpose, and in Part II not a line is given up to speculation or to misleading computations of future motion when this must at present be very uncertain. For several of the pairs in which a whole revolution has been completed the period only is stated, and for others for which orbits have been computed it is not even asserted that the mo- tion is orbital at all. As might be expected, Mr. Burn ham is equally conservative in regard to the presence of dark bodies which have been supposed to disturb the motion of the bright stars. That in ^Herculis is not even mentioned, while the indications of a long suspected third body in F 70 Ophiuchi are believed to be equally well explained by the ordinary errors of observation. When this great mass of material is examined Mr. Burn- ham finds the following general results: There are eighty- eight pairs for which orbits have been computed, of which, however, only thirty-four can be regarded as of any value. There are ninety-four systems which are certainly binary. There are 112 pairs which are probably binary, and thirty-eight pairs in which the two stars have different proper motions, as in the well-known system 61 Cygni. There are 585 pairs hav- ing common proper motion and 337 in which, from merid- ian-circle observations, proper motion has been observed in the principal star. Thus of the entire list of 13,665 stars there are but 879 for which a physical connection can at this time be inferred. No discussion is attempted of the distribution of these stars on the sky, nor is any attempt made to theorize on the construc- tion and extent of the stellar universe. While the discoveries and measures are still both so incomplete, it is the belief that all such generalizations are idle and useless. Mr. Burnh.\m strongly emphasizes the fact that what is wanted now for the advancement of double-star astronomy is not theories and speculations, or even extensive computations, but only careful, prolonged, and systematic observations with the telescope. It cannot be doubted that a great impetus will be given to obser- vations in this important branch of astronomy, and that their value will be exceedingly enhanced by the publication of this monumental work. Flower Observatory, University of Pennsylvania. NEW PUBLICATIONS. Berberich, a. Astronomisches Jahresbericht, Band VIII. Die Literatur des Jahres 1906. Berlin : Georg Reimer. 1907. 8vo. XXV -f- 672 pp. Paper. About 20m. Block, H. G. Tafeln zur Berechnung der Storungen einer Gruppe kleiner Planeten durch Saturn. Stockholm : 1907. 4to. 20 pp. Paper. BoHLiN, Karl. Der Zweite Sternhaufen im Hercules, Messier 92. Stockholm. 1906. 4to. 36 pp. Paper. BuRNHAM, S. W. A general catalogue of double stars within 121^ of the north pole. Part I, the catalogue; Part II, notes to the catalogue. Chicago: The Carnegie Institu- tion of Washington, 1907. 4to. Iv + viii + 1086 pp. Paper. CoMSTOCK, G. C. Observations of double stai;s. Madison: Publications of the Washburn Observatory, Vol. X, Part 3. 1907. 4to. 106 pp. Paper. Herz, N. Stern-Catalog fiir die Zone von 6° bis 10° siidlichen Declination filr das Aequinoctium 1890. Abth. I. Ab- handlungen der Koniglich Preussischen Academic der Wissenschaften, aus dem Jahre 1906. Berlin: Georg Reimer. 1906. 4to. 92 pp. Boards. Janssen, J. Observation de I'eclipse totale de soleil du 30 Aout 1905 a Alcosebre (Espagne). Annales de Tobservatoire d'astronomie physique de Paris. Tome troisieme, premiere partie. Paris: Gauthier Villiers. 1906. 4to. 20 pp. (plates). Paper. KoPFF, A. Ueber die Nebel der Nova Persei, Publikationen der Astrophysikalischen Instituts Konigstuhl-Heidelberg. Band II, No. 9. 4to. 27 pp. Paper. Ogburn, John H. Results of observations with the zenith telescope of the Sayre Astronomical Observatory, from September 11, 1904, to September i, 1905. South Bethle- hem: Lehigh University, Astronomical Papers, Vol. I, Part I. 1907. 4to. 46 pp. Paper. Schiller, Karl. Photographische Helligkeiten und mittlere Oerter von 251 Sternen der Plejaden-Gruppe. Publika- 224 Publications of the tionen der Astrophysikalischen Instituts Konigstuhl-Hei- delberg. Band II, No. lo. 4to. 26 pp. Paper. Seares, F. H. Finding ephemerides for Comet 1894 IV (E. Swift). Laws Observatory Bulletin, No. 12. Columbia: University of Missouri. 1907. 4to. 4 pp. Turner, H. H. Astrographic Catalogue 1900.0. Oxford Sec- tion, declination + 24° to + 32°. Vol. I, measures of rectangular co-ordinates and diameters of 65,750 star im- ages on plates with centers in dec. -f- 31°. Vol. II, meas- ures of the rectangular co-ordinates and diameters of 66,718 star images on plates with centers in dec. + 30° • Edin- burgh. 1906. 4to. xlvii 4- 223 and xlii + 232 pp. Paper. Annales de I'Observatoire Royal de Belgique. Tome IX, Fasc. II, Observations solaires effectuees a Uccle en 1904. Tome IX, Fasc. Ill, Observations faites a la lunette meridienne de Gambey en 1902, 1903, 1904, et 1905. Bruxelles. 1906. 4to. 108 and 313 pp. Paper. Publikationen des Astrophysikalischen Observatoriums zu Potsdam.. Photographische Himmelskarte-Katalog, Band IV. Potsdam. 1907. 4to. xiv + 5^9 PP- Boards. 25m. Solar Physics Committee. Spectroscopic comparison of metals present in certain terrestrial and celestial light sources. (With special reference to vanadium and titanium.) Lon- don : Wynian & Sons. 4to. 37 pp. Boards. 3s. Astronomical Society of the Pacific, 225 Minutes of the Meeting of the Board of Directors heuj AT the Students* Observatory, Berkeley, on July 13, 1907, at 7:30 p. m. President Gushing presided. A quorum was present. The minutes of the last meeting were approved. The following new member was duly elected: — Mrs. W. B. CuNNANE 1327 De la Vina St., Santa Barbara, Cal. The Treasurer reported that, by order of the Finance Committee, the following bonds had been bought and paid for from the savings hank deposits, viz.: Alexander Montgomery Library Fund (from Security Sav- ings Bank), Contra Costa Water Company $i,ooo Gold Bond No. 1665 $1,035.00 (Interest January and July; principal due January i, 1915.) Wm. Alvord Fund (from Savings and Ix)an Society), Contra Costa Water Company $1,000 (jold Bond No. 1666 $1,035.00 (Interest Jantiary and July; principal due January i, 1915.) Several replies to the circular letter concerning the library were read. Among other contributions to the library were two of cash. It was moved, carried, and ordered that these cash contributions be re- ceived, the money thus acquired to be expended for books, to be inscribed as the gift of the donors of said cash contributions. The following publications were ordered placed upon our exchange list :— The American Astronomer. The Journal of the Royal Astronomical Society of Canada. Replies, acknowledging w]th thanks the receipt of the award of the Donohoe comet-medal, from Dr. August Kopff, Rev. Joel H. Metcalf, and Mr. David Ross, were read. Professor R. G. Aitken, of the I.ick Observatory, was elected Sec- letary at Mt. Hamilton for the unexpired term. Upon motion it was Rtsotvtd, That the Committee on Publication be authorized to reprint the By- Laws, the Bruce Medal Statutes, and the Donohoe Comet-Medal Statutes. Adjourned. Minutes of the Meeting of the Astronomical Society OF the Pacific held at the Students' Observatory, Berkeley, on July 13, 1907, at 8 p. m. President Gushing called the meeting to order, and introduced the lecturer of the evening, Professor R. T. Crawford, of the Berkeley Astronomical Department, who read a paper on "Our Debt to As- tronomy." The Society was very fortunate in having present Professor Simon Newcomb, to whom (in 1897) the first award of its Bruce Medal was made. After the lecture by Professor Crawford, Professor Newcomb was introduced and entertained the Society with a most pleasing mformal address. At the close of the meeting the members availed themselves of the privilege of meeting Professor Newcomb. Adjourned. utcaltons of the Astronomical Society, OPFICBRB OF THE SOCIETV. Mr. Cbm. S. Ciisnr»o Preiidtat Mr. A. H. Baiicocii pJrM Viet'Pr4iidni Mr. W. W. Cahm[[.l Stce»d Vict-PrriiirHl Mr. Gio E. Hau Third yUi-Pritid*»t Mr. R. T. CiAwroiD (Smdenti' OlaervaloTy, Birkcler) Secrtlarj Mr. R. G. Aiiiuii (MounI Himillan. CL) Stcritary Mr. F. R. Zi£L Tr«a«r»f Board of DirtcloTi — Meuri. Atthih, Baicock, Bukckbaltu, Cahpiiu- Cuocsn. CiAwraan. CoaRiHC, Hau. Ricbaidkh. Towrlcv, Ziei- Fintici Commintt — Meisri. RicbaudA))!. Ciocin, Bu(ckhu.t>k. Commillit ait PHbiicalieti — M«Hr(. Ari»tll. Townle*. Newsus. Library Cavimitltr—iSttttt, CBAWroiir. Iivihd, Towslet. Cemm'llrr dh IIu Comel.JMtiiiiJ— Messrs. Cahmill (tx-aScio), ButCKHALTtL Pebkihi. NOTICE. The ■tiention of new meraberi ii called la Article VIII of the B^Laoa. vbicb provides that the innual lubtcriptian. paid on election, covera the catendar year calendar year. Thii rule i> neceisary in order to make our boobkecpinB ai sinple ■1 posaiblc. Dues BenI by mall ihauld be directed to Aationomlcal Secietv of the Pacific, Sludents' Observalory, Berkeley. It ia intended Ihac each nenilier of Ifae Soclet)' thall receive a copy of eieh one of Ibe Publicaliem lor Ihe year in which he was elected to membership and for all lublequent yearl. IE there have been (unfortunately) any omiltiona in thia mailer, It is requeated that Ifae Seerelariei be at once noiiRecf, in order that Ibe milling numbers may be lupplied, Memberi are requested to preserve the copies oE the Publiratisni of the Society as sent to them. Once each year a title-page and contents of Ihe preceding numbers will also be sent to Ibe membcti. wba can then bind the numbers together into a volume. Complete volumes for pax years will also be luppUed, to members only, to Ear as the stock in hand is sulficienl. on the payment of two dollars per volume lo either of the Secretaries. Any non-resident member ■'ilhin the United Slates can obtain booka from the Society's library by sending his library card with len cents in stamps to the Secretary A. S. P., Students- Observatory, Berkeley. Cal.. who will return the book and the card. The Committee on Publicalion desire* la aar that Ihe order in which papers are printed in Ihe PublicalioHi is decided simply by canvenience. In a general Papers intended la be printed in a given number of the P^biicllioH/ iSouidbc'in the bands nf the Committee not later than the aoth of the monlh preceding dale of publication. It is not possible to send proof sheets of papers to be printed ta lulhors whose residence is not within Ihe United Sutes. The responiibil it/ for the views expressed in ibe papers printed, and for the form of their expression, rests The lilies of' papers for resding should be cammunicaled to either of the Sec- rettries as early as possible, as well as any changes in addresses. The Secre- Ury in Berkeley will ncnd to any member of the Society suitable sUliaoery. alamped wllb Ihe seal of Ike Society, at com price, aa follows: a block of letter paper. 40 cents; of note paper, 3; cents; a package of envelopes, z; cents. These prices include postage, and should be remitted by money-order or in U. S. poaUge stamps. The sendinga are al Ihe risk oE the member. Those members who prapoK 10 attend Ihe meeting* at Mount Hamilton during Ibe summer should communicate with "The Secretary Astronomical Society ol the Pacific." Students' Observalory, Berkeley, Cal,. in order that arrangements m«y^._, . be made for transportation, lodging, etc. ^^I PUBLICATIONS ISSUED BI-MONTHLV. *^^H I PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XIX, San Francisco, California, October 10, 1907. No. 116. RECENT CHANGES AT THE OBSERVATORY OF THE D. O. MILLS EXPEDITION. By ITeber D. Curtis. When Mr. Mills provided for a continuation of the work of the D. O, Mills Expedition to the Southern Hemisphere for five years a number of improvements in, and additions to, the equipment were decided upon by Director Campbell, many of which had been suggested as desirable by the experi- ence of Professor W. H. Wright and Dr. H. K. Palmer during the course of their two-year period of work in Chile. It is the purpose of this paper to describe a number of the changes in the equipment which have been made since March, 1906, the date when Professor Wright returned to the United States, and the writer assumed charge of the station. Many of the minor improvements are not of such magnitude in themselves as to warrant extended notice; but if one takes into acONint the difficulty of accomplishment of all such alter- ations and additions on a hilltop not too easy of access, in a distant country, and without skilled labor, it can easily be realized that they have cost considerable effort. Mr. George F. Paddock, formerly Fellow at the Leander McCormick Observatory of the University of Virginia, arrived in San- tiago on August 2, 1906, and has taken an active part in the installation of all improvements made since that time. A small building, about fourteen by seventeen feet, was first built, about thirty feet to the south of the observatory dome. It contains a workshop and two small sleeping-rooms for the observers. The observatory is located 860 feet above the city and about one mile distant from the homes of the observers. This daily or nightly climb is a matter of much less bodily strain than would be thought, — after one is well hardened to it, — but there is no change which has contributed more to 228 Publications of the the comfort of the observers than the ability to be able to "turn in" immediately after a night's work. In the workshop have been placed a 12-inch Star engine-lathe of the new heavy model made by this company, a grinder-head, a work- bench, and an extensive collection of small tools, as well as a refrigerating machine, to which reference will be made later. The machinery is driven by a one-horsepower electric motor fastened near the ceiling. The electric line from the chy to the observatory was in part rebuilt and extended to oonnect with the circuit of the city's lighting system, and wires were also strung for telephone communication between the obierv- atory and the writer's home at the foot of the hill. Professor Wright had found the motion of the 37-inch reflector in declination a very difficult one. The axis was of steel, finely ground at the bearing surfaces, and running in babbitt, but such was the weight of the moving parts (about two tons) that much effort was necessary to set the telescope moving in this component. The force required to start the motion averaged fifty to one hundred pounds on the end of a 6. 1 -foot lever, dci^ending upon the hour-angle of the tele- scope. After consultation with the makers of the mounting, designs were drawn for roller bearings in each of the declination pillow-blocks, and a ball thntst bearing at the block farthest from the tclcscope-tube, lack of space preventing its use at the bearing nearest the tube. The new bearings are of the frictionless type manufactured by the Anti-Friction Roller Rearing CcMupany, of Los Angeles. As this company did not have the facilities for making such large bearings as were required in this case, free use of their patent was cour- teously granted by them to the makers of the mounting, the I'^ilton luiginc Works, of Los Angeles, for the construction of the roller bearings for the Mills reflector. The system for each bearing consists of tool-steel carrying-rolls three fourths of an inch in diameter, with an equal number oi alternating smaller rolls, whose only function is to obviat < the sliding friction between the larger carrying-rolls. Thea:"^ being nothing but rolling contacts, no lubricant is necessary**" Steel rings one fcairth of an inch square, fitting into groove::^ at each end of the rolls, are screwed to the axis, and, wil similar heckling rings outside the roller group fitting in tl same grooves, serve not only to prevent end-motion in th"^* Astronomical Society of the Pacific. 229 rolls, but to keep the smaller intermediate rolls in their correct positions. The rolls are eight inches long on the inboard, and five and a half inches on the outboard bearing. For the thrust a strong tool-steel sleeve was made to fit over the declination axis and a tool-steel bearing-ring provided to fit into a shallow recess in the outboard bearing. Between the two steel surfaces there moves freely a bronze ring pierced with seventy-two apertures, each of which contains a half-inch steel ball. The actual work of boring out the heavy bearing- Mocks from six and a half to eight inches diameter and recessing the outer block for the thrust-ring was done on the observatory's lathe. The results have proved very satisfac- tory, the ease of motion being remarkable. It now takes, at a distance of 6.1 feet from the center of motion, but six to nine pounds to start and maintain the motion in declination at all ordinary hour-angles, and only sixteen to nineteen pounds in the extreme case when the telescope is at six hours hour-angle directly over the polar axis. It is now quite easy to move the telescope in declination while looking through the finder with the hand on the corner of the cube only two and a half feet from the center of the declination axis pro- duced. With a centrally hung refractor-tube of the same weight and an available leverage of fifteen to eighteen feet, the very slight effort required to move the tube might even be a disadvantage. The responsiveness of the declination slow motion has likewise greatly improved. The Cassegrainian system of the 37-inch Mills reflector has from the beginning been subject to progressive focal changes in the first half of the night. These changes were always in the direction of increasing focal length, it being necessary gradually and continuously to increase the focal length of the telescoi^e during the first four or five hours of the night by amounts which reach totals of fifteen to twenty- five millimeters. It was decided to try artificial cooling of the mirror, in the hope that by reducing in advance the mirror temperature to that of the night these progressive focal changes might be greatly reduced or destroyed entirely. As a preliminary to the testing of the refrigeration the ventilation of the mirror in its cell was bettered. The great mirror has a clear aperture of 36.56 inches, is 5.5 inches thick at the center, and is pierced by a central hole 4.?>7 \tvcVve% vcv 230 Publications of the diameter. The cast-iron cell is about one half inch in thick- ness ; at the center of the back is a hole 8.5 inches in diameter, which was formerly generally kept closed with a cast-iron filler disk having a two-inch aperture for the passage of the light to the spectrograph slit. Aside from this aperture, and a few small ones for the adjusting screws of the mirror supports, the only other ventilating opening in the ironwork about the mirror was a small window six inches square cut in one side of the cube just above the mirror. The mirror cover, which had formerly rested nearly in contact with the mirror, was moved fourteen inches up the cube; the cube window was enlarged to six by sixteen inches and a similar window cut on the opposite side of the cube. Six holes, each 5.2 inches in diameter, were cut in the iron back of the cell, and the use of the filler-plate discontinued. The ventilating area at the back of the mirror is thus now about one sixth of the area of the mirror. During the past observing season record has been kept of the focal changes, and as a result of the study of these, in connection with the temperature variations, the. following general conclusions have been drawn with reference to the behavior of the mirror system without artificial cooling: — (i) The increased ventilation about the mirror has only slightly reduced the focal range in the first part of the night, the average under normal summer observing conditions being about fourteen millimeters. A position of focal equilibrium is probably reached somewhat earlier, all focal change ceasing as a rule bv four hours after sunset. (2) Silvering the back of the mirror, as recommended by Professors Wadsworth and Ritcuey, has had no appreciable effect in reducing the focal range. Insulating the sides of the hole in the primary mirror with blanketing has also been without effect. (3) The focus of the system after equilibrium is reached seems not to vary noticeably for different temperatures. (4) The focal changes have their origin in the large mirror, and not in the secondary ; this has been shown by tests on a number of nights by star-trails on an inclined photographic plate at the focus of the primary. These. showed a progressive lengthening of the focus of the main mirror by amounts ranging from 1.2"^"^ k) 2.2™™. As a focal change in the ( ■^ Astronomical Society of the Pacific. 231 primary produces 10. i times as much change in the focus of the entire system, these results are seen to be in good accord with the ranges secured for the system as a whole. Similar tiests on two evenings exposing alternately the inner and outer portions of the primary showed that the outer ring was about 1.2"" shorter focally than the inner zone, a differ- ence which vanished in similar tests made in the morning hours. (5) The relation connecting the focal changes of the mirror with the fall in external temperature is apparently a very complex one, many factors entering in. Frequently a drop of 2° C. between the temperatures of afternoon and early evening will cause as great a focal range as a drop of 6° C. In general, the rapidity with which a temperature change takes place seems to be of greater effect than its absolute magnitude. The system of refrigeration employed is the direct anhydrous ammonia method. The machine is the smallest of the regular commercial sizes of isolated cooling plants manufactured by the Bnmswick Refrigerating Company, of Bnmswick, N. J. It requires one horsepower to run it and the pump used for water circulation, and is rated by the manufacturers as having a capacity equal to that of the melting of one hundred pounds of ice per day. It is located in the shop forty-eight feet from the telescope pier, to one side of which are attached the cooling coils, three feet by two feet by six inches, of one-inch piping, and well insulated from the pier. The coils are con- nected with the ammonia machine by a double line of piping of one-fourth-inch bore, insulated with cork and felt. In use a removable wooden case lined with thick felt is rolled into position about the telescope; this case contains about eighty- five cubic feet and insulates from the outside air the spectro- graph, mirror, and lower half of the cube. Two electric fans keep the air in the case in constant circulation. The refrig- erating machine is entirely automatic in its action, and no difficulty is found in reducing the temperature within the case by 5® or 6° C. in a run of one hour and a half. After some experiments, the following procedure has been found most advantageous. Refrigeration is started about three hours before sunset and the temperature at the mirror reduced about 5^ C. The case is removed from the telescope about forty minutes before sunset; at this time the outside tem- perature is falling rapidly, and the mirror, at least in its outer 232 Publications of the portions, is colder than the air. Equilibrium is reached by sunset, or very shortly after, when focal tests almost invariably show the same value of the focus as that at which it had been left at the time of closing work on the night before. Focal changes are either entirely absent or small, being rarely greater than five millimeters. Sudden changes in the night temperature still produce focal changes of small amount. Fortunately the average temperature gradient during normal summer nights on Cerro San Cristobal is very regular; on quite a proportion of nights when cooling has been used there has been no focal change during the entire night. The change in the source of electric power rendered neces- sary the complete rewiring of the observatory, and use was made of this opportunity to arrange all the circuits used in the spectroscopic work in a switchboard on the front of the pier. To this switchboard come, underneath the floor of the dome, a circuit from three primary cells used with the relay for the heating of the spectrograph case; a circuit from four storage-batteries, held in reserve for the spark and used at present only for small lights to illuminate the divided circles; and the 220-vo]t circuit, used for heating the temperature case, for lights and for the arc comparison. Arc-comparison apparatus has lately been attached to the spectrograph, though the spark is held in readiness for special work; for this latter the condenser and self-induction can be cut in or out by switches. All the electrical circuits, including the high tension for the spark, are carried up over the axes of the telescope to a line of binding-posts near the mirror cell, to which flexible cord and convenient plugs are fitted, doing away with all use of binding-posts in actual work. A one-prism and a two-prism spectrograph have been added to the equipment. These are arranged to attach to the steel frame of the three-prism instrument by removing the box containing the three-prism train. They use the collimator, slit, comparison apparatus, and supporting tniss of the three- prism instrument. The prism-boxes and camera-tubes of the new spectrographs arc built up of strong brass plates, the general scheme of construction being that employed in the remounted Mills spectrograph at Lick Observatory. Tests have failed to show any flexure effects. The new camera- lenses are of the Ilartmann uncemented type, consisting of Astronomical Society of the Pacific. 233 three lenses with intervening air-spaces; the total thickness of glass traversed by the beam at the center of the lenses is 0.92 inch. The focal length of the camera for the two-prism instrument is sixteen inches, that for the one-prism eighteen inches. A special temperature-case fits either of the two new instruments. The heating arrangement is similar to that of the three-prism spectrograph, a mercurial thermostat on the steel body truss serving for all three instruments. It is Director Campbell's intention that radial-velocity determina- tions in the southern sky shall be carried down to fainter stars with the new instruments, but owing to the long delay in gaining possession of the lenses due to the congestion of business at Valparaiso following the great earthquake, no systematic work has yet been undertaken. Among minor additions to the equipment may be mentioned a new Toepfer measuring-engine and a Berolina calculating- machine. A photographic attachment has been fitted up to test the performance of the telescope in direct photography of clusters and nebulae. The resilvering of the mirror has been expedited by the building of a heavy wooden frame on wheels to withdraw the mirror and cell, and to support the mirror during the process of silvering. A convenient carriage has also been built to remove the spectrograph from the telescope. A card catalogue has been made to keep record of the results of the work; this is on the same plan as that used at Lick Observatory for the results from the northern sky. Mr. Mills's generosity in providing this increased equip- ment for the work of the next five years will add greatly to the comfort of the observers and the ease of manipulation of the instruments, besides materially enlarging the scope and quantity of the work. The present equipment, with spec- trographs of one, two, and three prisms, may be considered quite complete for general work in stellar spectroscopy and determinations of stellar velocities, and will render the velocity survey of the stars of the southern heavens much more complete and comprehensive, a result of great moment in improving our knowledge of the Sun's motion through space, and of the structure of our stellar universe. The D. O. Mills Expedition, Santiago, Chile, June, 1907. 234 Publications of the PLANETARY PHENOMENA FOR NOVEMBER AND DECEMBER, 1907. By Malcx)lm McNeill. PHASES OF THE MOON, PACIFIC TIME. New Moon Nov. 5, 2^ 39m p.m. First Quarter. . " 12,9 14 a.m. Full Moon " 19,4 4 P.M. Last Quarter.. . " 27, 8 21 p.m. New Moon Dec. 5, 2^ 22^ a.m. First Quarter.. " 11,6 16 p.m. Full Moon " 19,9 55 A.M. Last Quarter. . . " 27,3 10 p.m. The Sun reaches the winter solstice and winter begins December 22d, 4 p.m., Pacific time. Mercury is an evening star on November ist, not very far from greatest east elongation, which it passed late in October, but eastern elongations during the last half of the year g^ve a very poor opportunity for seeing the planet as an evening star. The interval between the setting of the Sun and of the planet is less than an hour on November ist, and diminishes steadily until conjunction in the early morning of November 14th. At this time Mercury is in transit across the disk of the Sun. The principal phases of the transit in Pacific time are as follows : — Ingress, exterior contact, November 14, 2^ 24" a.m. Ingress, interior contact, " " 2 26 a.m. Least distance of centers 12' 38" " "47 a.m. Egress, interior contact, " " 5 47 a.m. Egress, exterior contact, " " 5 50 a.m. The planet will pass over the north half of the Sun. It will be seen that the transit is practically over at sunrise in the extreme western part of the country, and therefore cannot be seen there, but the latter half of the phenomenon can be seen from the central and eastern parts, the Sun rising after the beginning of transit. The next transit will occur in 1914. Transits of Mercury are of little scientific interest. After November 14th Mercury is a morning star, and moves rapidly out toward greatest west elongation, reaching it on the morning of December 1st. It will then rise an hour and three quarters before sunrise, and the interval will not be less than an hour until some days after the middle of the month. It will therefore be an easy object to see in the twilight on Astronomical Society of the Pacific. 235 early December mornings. By the end of the month the planet will not be far from superior conjunction with the Sun. Venus is an evening star throughout the month, and shortly after November ist remains above the horizon long enough after sunset to be easily seen in the evening twilight. On December ist the interval is a little more than an hour, and by the end of the month it has increased to two hours. Although it is in the part of its orbit farthest from the Earth, it will be a conspicuous object in the evening twilight. Mars, although it has lost very much of its brilliancy, is still a conspicuous object in the southwestern sky in the evening. During November and December it changes its time of setting only twenty-four minutes, from 11** 11"* p.m. to 10^ 47" P.M. It moves 38° eastward and 16° northward from the middle of Capricorn through Aquarius into Pisces. On the morning of December 31st it is in conjunction with Saturn, passing 1° 50' north of that planet. During the two months its distance from the Earth increases from 85 to 127 millions of miles, and its brightness at the end of the period is less than one half of that at the beginning, but it is in a region barren of bright stars, and there will be no difficulty in identifying it. Saturn is the only bright object near, and its dull yellow color distinguishes it easily from the ruddy color of Mars. Jupiter rises a little before 11** 30" p.m. on November ist, at 9^ 30" P.M. on December ist, and at about f" 20"* p.m. on December 31st. It is therefore getting around again into good position for evening observation. It moves about 5° eastward and 1° southward up to the end of November, and during December moves a little westward in the constellation Cancer, Saturn sets somewhat earlier, but still remains in good posi- tion for evening observation. On November ist it sets at about 2** 30™ a.m., on December ist at about 12^ 30" a.m., and on December 31st at about 10^ 30™ p.m. It moves westward a little up to November 25th, and then moves eastward, making about 1° by December 31st. It is in the western part of the constellation Pisces. Throughout the two months the Sun and the Earth remain on opposite sides of the plane of the rings, and we look toward the dark face, but by the end of December the Earth has nearly, reached the plane of the rings once more, and they are nearly edgewise toward us. 236 Publications of the During January the Earth will cross the plane and be on the same side as the Sun. This condition of affairs will then continue for fifteen years. Uranus is in the southwestern sky in the evening, setting a little after 8^ 30™ p.m. on November ist, at 6** 45"* p.m. on December ist, and at 4^ 56™ p.m. on December 31st, only a few minutes after sunset. It will reach conjunction with the Sun early in January, 1908. Its faintness and low altitude will make it a difficult object to see at any time during the two-month period. It is still in Sagittarius, and moves about 3° westward. On December nth it is in conjunction with Venus, the latter being 59' to the south. Neptune is in Gemini, and rises about 9 p.m. on November 1st and at about 5 p.m. on December 31st. (FIFTY-NINTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-!Medal of the Astronomical Society of the Pacific has been awarded to M. Giacobini, of Nice, France, for his discovery of an unexpected comet on March 9, 1907. Committee of the Comet-Medal : W. W. Campbell, C. D. Perrine, San Francisco, September 23, 1907. CllAS. BuRCKHALTER. (SIXTIETH) AWARD OF THE DONOHOE COMET- MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to Mr. Mellish, of Madison, Wisconson, for his discovery of an unexpected comet on April 14, 1907. Committee of the Comet-Medal : W. W. Campbell, C. D. Perrine, San Francisco, September 23. 1907. Chas. Burckhalter. Astronomical Society of the Pacific, 237 (SIXTY-FIRST) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to M. Giacobini, of Nice, France, for his discovery of an unexpected comet on June 2, 1907. Committee of the Comet-Medal : W. W. Campbell, C. D. Perrine, San Francisco, September 23, 1907. Chas. Burckhalter. (SIXTY-SECOND) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to Zaccheus Daniel, of Princeton, New Jersey, for his discovery of an unexpected comet on June 9, 1907- Committee of the Comet-Medal : W. W. Campbell, C. D. Perrine, San Francisco, September 23, 1907. Chas. Burckhalter. 238 Publications of the Astronomical Society, &c. t HERMANN CARL VOGEL. f It is with the deepest regret that the Astronomical Society of the Pacific has learned of the death, on August 14th, of one of the world's most distinguished astronomers, Geheimer Ober- Reg. Rath Professor Doctor Hermann Carl Vogel, Director des Astrophysikalischen Observatorium zu Potsdam, Germany. His death comes as a great blow to astronomical science, as he was one of the most industrious, resourceful, and pro- ductive investigators, in spite of the fact that his health had been rapidly failing during recent years. His achievements, well-known to every student in astronomy, will serve as his monument in ages to come. The members of the Society will recall with satisfaction the glowing tribute paid to Vogel by our past President, Professor Townley, at the annual meeting in the year 1906, in bestowing upon him the Bruce Medal in behalf of the Society.^ Those of us who had the rare fortune of a closer personal acquaintance with him learned to admire his noble character no less than his immortal services to astronomy. Vogel, first of all, was a man in the tnie sense of the word, an astrophysicist next. Kind to those who sought his help and advice, charitable in controversy with those who held opposing views in scientific matters, loyal to his staff, gener- ous to his cor workers, faithful and self-sacrificing towards his students, he endeared himself to all who came in contact with him. It is a source of deep satisfaction to the Astronomical So- ciety of the Pacific that in making its last award of the Bruce Medal to Vo(;el it had the opportunity of expressing to the dis- tinguished deceased the high esteem in which his name was held in this country. A. O. Leuschner. Berkklkv Astronomical Department, Oct. 2, 1907. ' Address of the Retiring Presitlent of the Society in .\warding the Bruce Medal to Geheimer Ober-Reg. Rath Professor Doctor Hermans Carl Vogel. By Sidney Dean Townley. Publications A. S. P., Vol. XVIII, No. 107. NOTES FROM PACIFIC COAST 01iSER\'ATOKIES. Notes on the Eclipse Expeuition to Flint Island. The personnel of the Crocker EcUpse Expedition to Flint Island will consist of Director Campbell, Astronomer Per- RixE, Astronomer Aitkkn, Assistant Alrrecht, of the Lick Observatory Staff, and Professor E. P. Lewis, of the Depart- ment of Physics of the University of California. The observers of the Smithsonian institution Expedition will consist Qf Director C. G. Abdot and Mr. Alfred Moore, of the Univer- sity of California. The carpenter, two workmen, cook, and cook's assistant will bring the total number up to twelve, to which the Commander of the U. S. gunboat ".Annapolis" de- sired the party to be limited. The expedition exjxicts to sail from San Francisco on November 22A, and return on January 25th. F. K. McClean, Esq., of Tunbridge Wells, England, expects to carry an expedition to Flint Island in a chartered vessel. It will be a pleasure for us to have him and his colleagues as associates on the island. Meteorological data collected during the month of January, 1907, are very encouraging. The eclipse will occur at about 11:18 A.M. At this hour of the day the sky was clear and fine on about twenty-two days in the month. Mt. Hamilton. September ii,, 190?. W. W. Campbell. Spectba of the Limb and Center of the Sun, In a comparative study of the spectrum of the Sun at the center and near the limb, the following points of difference have been found : — 1. The great majority of the lines that are strengthened in sun-six)ls are strengthened near the limb. 2. The great majority of the lines that are weakened in spots are weakened near the limb. 240 Publications of the 3. Most of the lines are slightly widened. 4. The wings of diffuse lines are greatly reduced. 5. In agreement with Halm, most of the lines are shifted toward the red. 6. The amount of the shift varies for different lines of the same element. 7. The lines of the ultra-violet cyanogen fluting are not shifted. In general, while the results so far obtained point to in- creased effective pressure near the limb (Halm's explanation) as the probable cause of the line-shifts, judgment is reserved until the completion of laboratory experiments now in progress. September, 1907. GeoRGE E. HalE, and WALTER S. AdamS. Preliminary Photographic Map of the Sun-Spot Spectrum. A photographic map, extending from A 4600 to A 7200, and consisting of 26 sections of 100 Angstroms each, has recently been made by Mr. Ellerman from the Mt. Wilson negatives of sun-spot spectra. The original negatives were made with the Littrow-grating spectrograph, of eighteen feet focal length, used with the Snow telescope. Each section of the spot spectrum, after being enlarged on a plate moving in the direction of the lines (by the pendulum process frequently employed for widening stellar spectra), is printed alongside the corresponding region of the normal solar spectrum. An approximate scale of wave-lengths, merely for the identification of lines, and not for the determination of their positions, also appears on each section. It is expected that a more perfect map can be issued later. This is intended to supply the imme- diate needs of visual observers of spot spectra, and has been I)laccd in the hands of those who are taking part in the work set on foot by the International Union for Co-operation in Solar Research. ^ t^ tt George E. Hale. September, 1907. Six Stars Whose Radial Velocities Vary. The following stars have been shown to have variable radial velocities, by photographs taken with the Mills spectrograph at Mt. Hamilton. The approximate range of speed observed Astronomical Society of the Pacific. 241 is given in the second column, and the names of the discoverers in the third : — Star. 0 Tauri f Tauri If Camelopardalis A Bootis P Corona: i Cygni Observed Range. Observed bf — I S to — 24^™ Moore. + 9 -\- 2y Moore. + 22 — 40 Moore. — II — 40 Moore. IS 33 Moore. — 19.6 — 24.1 Campbell. W. W. Campbell, J. H. MooRE. Two Stars Whose Radial Velocities Are Variable. Professor Wright, formerly in charge of the D. O. Mills Expedition to the Southern Hemisphere, has found from their variable velocities that the following stars are spectroscopic binaries : — X Carina, with observed speed lying between + 3.3^™ and + 17.4*'*" per second. i Gruis, with observed speed lying between — 2.3^™ and — 18.8^™ per second. The photographs upon which these discoveries were based were taken at Santiago, Chile, by Messrs. Wright and Palmer in 1904-1905, and by Dr. Curtis in 1906-1907. W. W. Campbell. Note on the Publications of the Lick Observatory. In the past years six quarto bound volumes of the Publi- cations of the Lick Observatory have been printed and dis- tributed to our correspondents. Volume VII of the Publications will contain articles written by members of the Berkeley Astronomical Department. Parts I, 2, and 3, relating to a short method of determining orbits, were printed in 1902. Only a few copies were mailed, to those who were especially interested in the subject, and the remainder of the edition was held with the expectation that the succeeding parts of the volume would be published soon and be included in the bound volume. Delay in completing the volume makes it desirable that these parts should be distributed unbound in the near future, following the completion of Parts 4 and 5, now ready to go to press. 242 Publications of the Volume VIII of the Publications, to contain photographs of nebulae and star clusters secured by the late Director Keeler and by Dr. Perrine, has been in preparation for three years past. In common with the experience of others, difficulties have been encountered in securing satisfactory reproductions of the photographs. It has been found necessary to compro- mise between pictorial effects and strict scientific values, and a fair rate of progress has been made during the past year. It is hoped that means will be found in the near future to make several complete sets of positives on glass of these photographs for deposit with leading scientific societies in various centers of population, in order to make them available to all investi- gators who desire to study them in detail. Volume IX of the Publications relates to the work of the D. O. Mills Expedition to the Southern Hemisphere. Parts I, 2, and 3 have just been mailed to our correspondents. They include an account of the organization and history of the expedition by Director Campbell, and a description of the instruments and methods by Acting-Astronomer William H. Wright, in charge of the expedition. The spectrograms secured by the expedition will have been measured and reduced in the course of a few months, and it is planned to publish the results for the 145 stars included in the programme as promptly as possible. Volume X of the Publications is more than half through the press. It contains the results of meridian-circle observations by Astronomer R. H. Tuckkr. The bound volume will be mailed before the end of the present year. It is the intention to send out all completed volumes in bound ^ , W. W. Campbell. Mt. Hamilton, September 23, 1907. A Fireproof Building on Mt. Hamilton. The construction of the half of a fireproof building is under way at the present time. It is not expected that the second half of the building will be constructed before the summer of 1909. The first half will contain, on the first floor, storage vaults for the valuable and extensive collection of observatory photo- graphs, together with the records and computations for all the observations, visual as well as photographic, and such valuable smaller instruments as are not in daily use. The Astronomical Society of the Pacific. 243 second floor will consist of a photographic-enlarging room, fifty feet in length in the clear, provided with graduated steel track to carry the lenses and cameras used in this work. It is expected that these rooms will be available for occupation about January ist. W. W. Campbell. Mt. Hamilton, September 23, 1907. Improvements to the Crossley Reflector. Mr. F. G. Pease, recently assistant to Professor G. W. RiTCHEY, and now optical expert to The Scientific Shop, Chicago, spent a month on Mt. Hamilton figuring a convex hyperbolic mirror for the Crossley reflector, in order to con- vert it into the Cassegrain form with an equivalent focal length of seventy-five feet. The corresponding mechanical additions are in course of construction by the Lick Observatory instrument-maker. It is hoped to utilize the Cassegrain fonn in parallax and spectrograph ic resear(^ies. Mt. Hamh-ton, September 23, 1907. W. W. Campbell. Recent Progress in the Construction Work of the Solar Observatory. The figuring of the 60-inch mirror was completed by Pro- fessor RiTCHEY in August, the residual errors not exceeding one tenth of a wave. The final tests were made with the aid of parallel light furnished by a 36-inch plane mirror, also fig- ured in our optical-shop during the year. The various convex and plane mirrors required for the 60-inch reflector when used in the Newtonian and Cassegrainian forms are now being completed. The mounting for this telescope will soon be finished in our instrument-shop. It is being assembled in Pasadena, and will be thoroughly tested there before being set up on Mt. Wilson. The Mt. Wilson road was finished in May, and much of the structural steel for the building and dome of the 60-inch reflector has been taken to the summit. The erection of the building is advancing rapidly under the supervision of Mr. George D. Jones, who also completed the road. The vertical coclostat telescope, of twelve inches aperture and sixty feet focal length, has been erected on the mountain, and will be tested in September. The ccelostat and second mirror support by Brashear and the 30-foot Littrow-grating 244 Publications of the spectrograph by Gaertner are in position, and the two plane mirrors, each twelve inches thick, have been figured by Pro- fessor RlTCHEY. ^ T- XT George E. Hale. September, 1907. Professor Julius's Visit to Mt. Wilson. As the outcome of a plan arranged two years ago, Professor W. H. Julius, of the University of Utrecht, has recently spent some weeks on Mt. Wilson. The prime object of his visit was to discuss the possible bearing of anomalous dispersion on astrophysical phenomena, in the hope that definite criteria might be found, capable of settling the question. A series of investigations has now been planned, covering both solar and laboratory work, and will be carried out as soon as possible. While on Mt. Wilson Professor Julius employed the five- foot spectroheliograph ^o photograph the anomalous-dispersion phenomena of sodium vapor, which resemble the solar flocculi. This work, as well as the numerous discussions of the anomalous-dispersion theory, was a source of great pleasure and profit to all the members of the staflf. September, 1907. GeORGE E. Hale. New App(;intments to the Stai-k of the Mt. Wilson Solar Observatory. Professor J. C. Kaptevx, of the University of Groningen, will hereafter spend several months of each year at Mt. Wilson, and take charge of such parallax and other similar work as may be done in connection with his "Plan of Selected Areas.'' So far as possible, the working programme of the 60-inch reflector will be arranged so that the photographs, both direct and spectrosco])ic, will be of service for Professor K.aptevx's studies of stellar distribution, as well as for the prime purpose of the observatory — the investigation of stellar evolution. This can easily be done by giving preference to Kapteyn's areas when undertaking general spectrographic surveys or in study- ing the smaller sjMral nebulT. In addition, certain nights will be set a])art for his s])ccial iniri)oscs. The direct bearing, on the (^ne hand, of Kaptevx's important researches on the problem of stellar evolution, and the need, on the other, of a larj^e reflector to furnish the data he desires for the fainter Astronomical Society of the Pacific. 245 stars, promise valuable returns from this co-operative under- taking. Professor Kaptevn will commence work on Mt. Wilson as soon as the 60-inch reflector is ready for use, probably in the summer of 1908. Dr. Arthur L. King, of the University of California, will take charge of the physical laboratory of the Solar Observatory as soon as he can relinquish the duties of his present position, probably in January, 1908. It is proposed to undertake an extensive investigation of anomalous-dispersion phenomena, and the effects of temperature and pressure, for lines which will also be studied in sun-spots, at the center and limb of the Sun, in the chromosphere, and in stars of various types. Dr. King will be assisted in the laboratory by Dr. Olmsted, who has been engaged in similar work at Mt. Wilson during the past year. ^ t- tt ^ -^ George E. Hale. September, 1907. Request for Unpublished Observations of the Variable Star U Geminorum. Mr. J. VAN der Bilt, Astronomer at the observatory, Utrecht, Holland, has undertaken the definitive reduction of all available observations of this remarkable variable, and would be very glad to have copies of any unpublished observa- tions, in such detail that they can be reduced by a normal photometric light-scale. They may be sent to him direct. Address Maliesingel 58, Utrecht; or if sent to the under- signed, they will be transmitted to him. Yerkes Observatory, J. A. Parkhurst. WnxjAMS Bay, Wisconsin. Changes in the Staff of Lick Observatory. Mr. Keivin Burns, Carnegie Assistant during the past four years, with duties in the measurement and reduction of stellar spectrograms, resigned, to take effect October ist, in order to pursue postgraduate studies. Dr. B. L. Newkirk, Carnegie Assistant during the past year, resigned, to take effect September ist, to accept appoint- ment as Assistant Professor of Mathematics and Mechanics in the College of Engineering, University of Minnesota. Henry C. Plummer, M. A., Assistant in the University of Oxford during the past six years, has been appointed a Fellow 246 Publications of the in the Lick Observatory. His time will be devoted to work in the spectroscopic department. Miss Leah Allen, of Brown University, Providence, Rhode Island, has been appointed Carnegie Assistant with duties in the measurement and reduction of spectrograms. Mt. Hamilton, September 23^ 1907. W. W. CAMPBELL. Ephemerides for the WatSon Asteroids. In accordance with the intention expressed in Lick Obscrva- tory Bulletin No. 114, to provide regularly ephemerides for coming oppositions of the various asteroids discovered by Watson, as far as the progress made in determining their elements and first order perturbations by Jupiter may permit, ephemerides were computed by Miss Glancy from the ele- ments and perturbations derived under my direction in the Berkeley Astronomical Department, for the recent oppositions of (103) Hera a.nd (179) Klyt(emnestra, Unfortunately, these ephemerides were not completed in time for publication in a Lick Obseri'atory Bulletin, A photographic position of Hera was secured, however, by Miss Glancy, at this observatory on June 14th, and requests for observations of (179) were sent to Director Campbell, of the Lick Observatory, and to Admiral Walker, Superintendent of the United States Naval Observatory. At the Lick Observatory three observations were secured by Mr. Duncan, on September i8th, 19th, and 20th, and Pro- fessor Eichelrerger, of the Naval Observatory, has commu- nicated to me a correction to the ephemeris of (179), based on an observation by Mr. Hammond, taken September 23d. In each case the ephemerides were given to i* and o'.i. The agreement between theory and observation is far better than was expected. The correction to the ephemeris of (103) on June 14th, is -\- o^6 and — o'.3. The correction to the ephem- eris of (i/O)* communicated by Professor Eichelberger for September 23(1, is +2^ and — o'.i. The mean correction, however, to the ephemeris of (179) from the Lick observa- tions, September 19th, is o^ and — o'.i. The last opposition upon which the elements of (179) are based occurred eight years ago. A. O. Leuschner. Berkeley Astronomical Department, Oct. 2, 1907. Astronomical Society of the Pacific. 247 Courses in Astronomy. The first term of the academic year 1907-1908 has opened with an increased enrollment in the courses in Practical Astron- omy. There are now forty-six students engaged in night work. Of these twenty-two take the course 4B, especially intended for civil engineers; eight are enrolled in 4A, a course designed for students who have chosen astronomy for their profession; and sixteen in Astronomy 2,. a general course offered to stu- dents as a culture study. Other enrollments during the current term are: General Astronomy, ninety-five; Least Squares, thirty-six; Interpolation, Numerical Integration, and Differen- tiation, six; Theoretical Astronomy (Graduate), three; Celes- tial Mechanics (Graduate), four. Of the graduate students, four are men and three women. In the undergraduate courses there is a notable increase this year in the percentage of men. The number of well-prepared, capable, and serious students in the various courses is also noteworthy. In view of the in- creased enrollment in the practical courses, the university has granted the department an additional assistant. Applications for the newly created position should be sent without delay to the Director of the Students' Observatory. A. O. Leuschner. Berkeley Astronomical Department, Oct. 2, 1907. GENERAL NOTES. Deaths. — During the last few months astronomy in central Europe has suffered a severe blow through the loss of four persons closely associated with the progress of the science in recent years. The Astronomisclie Nachrichten, No. 4190, con- tains three obituary notices. In the last number of these Publications brief mention was made of the death of Dr. Egon von Oppolzer, professor of astronomy at Innsbruck. Dr. Oppolzer, son of the noted astronomer Theodore von Oppolzer, author of the celebrated "Lehrbuch zur Bahn- bestimmung der Kometen und Planeten," was bom in Vienna on October 13, 1869, and died June 15, 1907, being therefore less than thirty -eight years of age. His education was obtained at the universities of Vienna and Munich. For a time he served as an assistant in the observatory at Prague, and in 1901 was made associate professor of astronomy at Innsbruck, and professor in 1906. Dr. Oppolzer was an enthusiastic investigator, and made many contributions to the science of astronomy along various lines. He made investigations con- cerning the Earth's atmosphere and solar phenomena. He was also interested in photography and photometry, and will be remembered as the discoverer of the short-period variability in the brightness of the planet Eros. During the last few years Dr. v. Oppolzer was engrossed in the building and equipping of a new observatory at Innsbruck, nearly the whole cost of which was paid out of his own pocket. The equipment was designed especially for work in spectroscopic and photo- graphic lines, and was almost ready for use when the hand of death intervened to bring to a sudden close the life and work of an ardent searcher for truth. On June 29th Professor Siegfried Czarpski, Director of the Carl Zeiss firm, makers of the celebrated Zeiss lenses and opti- cal instruments, died in Jena at the age of forty-six years. Although not an astronomer by profession, yet Dr. Czarpski, through his connection with the optical works and through attendance upon the meetings of the Astronomische Gesell- schaft, came into contact with many of the astronomers of Europe. When a young man he was a student under Helm- iiOLZ, and through the recommendation of that master became Astronomical Society of the Pacific. 249 private assistant to Professor Abbe. The balance of his life was spent in Jena. Dr. Czarpski's chief contribution to sci- ence is a book on geometrical optics, called "Theorie der Optischen Instrumente nach Abbe." On July 13th Dr. Heinrich Kreutz, associate professor of astronomy at the University of Kiel and editor of the Astro- nomische Nachrichten, passed away, after a long illness, at the age of fifty-two years. His preparation for the astronomical profession was obtained at the University of Bonn under the tutorship of Schonfeld and Krueger. After further study in Vienna under Weiss and Oppolzer, he became a computer in the Recheninstitut at Berlin. Dr. Kreutz soon gave up this position, however, in order to accept the position of observer and computer at the Kiel Observatory when Professor Krue- ger was called there in 1883 to become director of the observ- atory and editor of the Astronomische Nachrichten, In this position Kreutz became familiar with editorial work, and was naturally chosen to succeed Krueger in the editorship of the Nachrichten when the latter died, in 1896. The laborious duties of this position were performed with great care, and Professor Kreutz succeeded in maintaining the high standard previously enjoyed by the Nachrichten as the leading astro- nomical journal of the world. Dr. Kreutz was especially interested in the investigation of orbits of comets, and carried to completion several very extensive pieces of computation. The most important of these were investigations of the orbits of the comets 1843 I» 1861 II, 1880 I, 1882 II. Another severe loss to astronomy came through the death on August 13th of Professor Hermann Carl Vogel, Director of the Astrophysical Observatory at Potsdam. Dr. Vogel was the sixth Bruce medalist of the Astronomical Society of the Pacific, and reference to his life and work will be found on another page of this number of the Publications, Notes from "Science.*'^ — Mary W. Whitney, professor of astronomy at Vassar College, and president of the Nantucket Maria Mitchell Association, spent a week lately at the Maria Mitchell Memorial on Nantucket, giving instructive talks to members and their guests on "Maria Mitchell" and on "Recent Discoveries in the Solar System." Professor Whitney has appointed a building committee to consider plans for an observ- 250 Publications of the Astronomical Society, &c. atory to house properly an equatorial telescope recently donated to the association. Already the sum of $2,138 has been sub- scribed, and the association in charge of the memorial hopes for subscriptions to enable it not only to house the telescope but also to equip the observatory so that it may be available for astronomical classes in the near future. Sir David Gill's Address. — The presidential address of Sir David Gill, delivered before the annual meeting of the British Association for the Advancement of Science at Leicester, has been printed in full in Science for August i6th. The address is highly interesting and instructive, and should be read by every one interested in astronomy. Docto/s Degrees. — In Science for August 30th there is an article entitled ''Doctorates Conferred by American Universi- ties." During the last ten years the degree of Doctor of Philosophy and Doctor of Science (not including honorary degrees) has been conferred upon 2,715 persons, and of these 1,232 were taken in the sciences. Thirty-four degrees have been granted in astronomy, which stands ninth among the twenty sciences enumerated. Three doctorates in astronomy were conferred during the last academic year, as follows: By Columbia University, on Anne Sewell Young, "The Stellar Clusters // and x^^''-^*'/; Measurement and Reduction of the Rutherford Photographs" ; by the University of California, on James Davis Maddrill, "A Study of Several Stars of the 8 Cephci Type" ; by the University of Virginia, on Frank Walker Reed, ^'Singular Points in the Approximate Develop- ment of the Perturbative Function." NEW PUBLICATIONS. Ambronn, L. J., and R. Stemverzeichnis enthaltend alle Sterne bis zur 6.5tn Grosse fiir das Jahr igcxj.o. Berlin : J. Springer. 1907. Large 8vo. x + 183 pp. Cloth. Campbell, W. W. A list of Lick Observatory negatives from which lantern-slides and transparencies can be supplied. Sacramento. 1907. Svo. 21 pp. Paper. Cowley, Elizabeth B., and Whiteside, Ida. Definitive orbit of Comet 1826 IL Kiel: Astronomische Abhandlungen als Erganzungshefte zu den Astronomischen Nachrichten, Nr. 13. 1907. 4to. 18 pp. Paper. Dyson, F. W. Determinations of wave-length from spectra obtained at the total solar eclipses of 1900, 1901, and 1905. London: Memoirs of the Royal Astronomical Society, appendix to Vol. LVIL 1906. 4to. 50 pp. Boards. HuGGiNS, Lady. Agnes Mary Gierke and Ellen Mary Clerke : An appreciation. London: Printed for private circula- tion. 1907. 8vo. 54 pp. Cloth. Langley, Samuel Pierpont. Memorial meeting, December 3, 1906. Addresses by Doctor White, Professor Pickering, and Mr. Chanute. Washington; Smithsonian Miscella- neous Collections, No. 1720. 1907. 8vo. 49 pp. Paper. Palisa, Johann. Katalog von 3,458 Sternen fiir das mittlere Aequinoktium 1875.0. Vienna. 1906. 4to. xii -\- 95 pp. Paper. Schorr, R. Tafel der Reductions-Konstanten zur Berechnung scheinbarer Sternorter fiir die Jahre 1850 bis i860. Ham- burg: Mitteilungen der Hamburger Sternwarte, Nr. 9. 1907. Large 8vo. viii + 230 pp. Paper. Schwarzschild, K. Ueber die totale Sonnenfinsternis von 30 August, 1905. Gottingen: Astronomische Mitteilungen der K. Sternwarte zu Gottingen, 13 Teil. 1906. 4to. 73 pp. Plates. Paper. Taylor, H. Dennis. A system of applied optics. London: Macmillan & Company. 1906. Royal 8vo. 16 -{- 334 pp. Qoth. 252 Publications of the VoGEL, H. C. Die zwei Doppelrefraktoren des Observatori- ums. Potsdam: Piiblikationen des Astrophysikalischen Observatoriums zu Potsdam. Band 15, erstes Stuck. 1907. 4to. 59 pp. Plates. Paper. Berliner Astronomisches Jahrbuch fiir 1909. Berlin: Ferd. Diimmler. 1907. 8vo. x + 6i5pp. Paper. Connaisance des temps, pour Tan 1909. Paris: Gauthier- Villars. 1907. 8vo. viii +931 pp. Paper. 4 francs. Memoire del R. Osservatorio Astronomico al CoUejio Romano. Series III, Vol. IV, Parte II. Rome: 1907, 4to. 285 pp. Paper. Proceedings (The) of the optical convention. No. I. London. 1905. London: Norgate and Williams. Royal 8vo. vi + 247 pp. Cloth, 10 s. Publications of the Lick Observatory.^ Volume IX, Parts i, 2, and 3. Sacramento. 1907. 4to. 70 pp. Paper. *■ See note on page 241. Astronomical Society of the Pacific. 253 Minutes of the Meeting of the Board of Directors, Held AT the Lick Observatory, Mt. Hamilton, on September 14, 1907, at 8 p.m. President Gushing presided. The following directors were present: AiTKEN, Campbell, Crawford, Cushinc. Richardson, Townley, and ZiEL. The minutes of the last meeting (July 13, 1907) were approved. The Librarian reported many more generous responses to the circular letter concerning the library. A reply, acknowledging with thanks the receipt of the award of the Donohoe comet-medal, from Professor H. Thiele was read. The Library Committee was authorized to procure a card-catalogue case and an accessions-book. On behalf of the Committee on the Donohoe Comet-Medal Professor Campbell, chairman, reported the following awards : — To GiACOBiNi for the discovery of Comet a 1907; to Mellish for the discovery of Comet ^1907; to Giacoiuni for the discovery of Comet c 1907; to Daniel for the discovery of Comet d 1907. The resignation of Dr. Newkirk from the Pubhcation Committee was accepted with regret. Dr. James D. Maddrill was elected to fill the vacancy on the Publication Committee, rice Newkirk resigned. The Committee on Meetings, consisting of Messrs. Campbell, Leuschner, and Townlev, was continued, and requested to report at the next meeting. The following was elected to membership : — B. L. HoDGHEAD, 601 Merchants Exchange, San Francisco. The following was elected an institutional member : — Library of University of Washington, Seattle, Wash. The following were elected corresponding members : — Library of Solar 01)scrvatory, Mt. Wilson, Gal. Flower Observatory, University of Pennsylvania, Upper Derby, Pa. The following resolution was introduced and passed unanimously: — Resolved, That the bonds belonging to this Society be deposited in trust with the Mercantile Trust Company of San Francisco, a corporation, the said Trust Company to collect the interest and pay the same as it accrues to the Treasurer of this Society, the said bonds to be delivered by said Trust Company only as directed by this Society, the intention of the Society to remove the same from the custody of said Trust Company to be evidenced by a resolution of the Board of Directors, under seal of this corporation, and duly certified by the President, or a Vice-President, and the Secretary of the Society. Be it further Resolved, That the President and Treasurer of this Society are hereby authorized to take all necessary steps to carry this resolution into full force and effect, including, if necessary, the indorsement by them of any of the bonds belonging to this Society. A vote of thanks to the Director and Staff of the Lick Observatory for their invitation and hospitality at this meeting was passed unani- mously. Adjourned. 254 fubltcattons of the /Ijtronomtcal Hociety, ■ OFFICERS OP THB SOCISTV. Mr. Ch«s. S. CuiHtHc .PriiUtt Mr. A. H. Bmcock Firil Vic.-Frtodtm Mr. W. W. Campmu, Stcend t' Mr. G«i E. Hale Third V Mr. R. T. Cmawfou) (SluHcnli- Ohnrrvilory, Brrkele)') .Secrtttrj Mr. R. G. AiTKMH (Uount Huniltoa. Cal.) Src Mr. F. R. ZiEL TrtaMm Boaid of DiricloTi — Mosra. AiTiLtn, Bmcdci, Buicihaltbi, CAMfREU., Cukcee, CiMWFaaD, CualiiNO. Hale. Richaidion, Tdwhlev, Ziil. Finaiiee Cemmitlte — Mcun. Richaid. 1 NOTICE. The alLcnIlon of new membcrt !* called Xo Article Vltl of Ihe By-Laws, which provides lliat Ihe aanui! subscription, paid on eLeclion. covers [he ciFenilar year calendar Tear, Tbia rule is necessarr in order lo nuke our buokkeepinE sg simple Pacific, StudenO' Observatory. Berkeley. II is intended th»l ench raeteber of lie Soelely sfaidl reeeive a capy of each one matter, it it requested thai the Secretariei be at once notified, in order thai Ibe misiinc nombera may be supplied. Members ate requested to preserve Ihe coniei contenU of (be preceding numbers will also be lent to the members, who can then bind Ibe outnbers logetber inio . volume. Complete volumes for psst years will 1 also be supplied. 1o members only, so far as the stock in hand i> wffident. on the ' mil^' wilhto" the United' Suw^^cSn 1!t«in''bp!)te £"m"tbrSoeiely'a'"l"b™r^ "bi sending bis library carti wich ten cents in stamps to the Seeretarr A. S. P.. bludents- Ubservsloiy. BerkeleT. Cal„ who will return the book sod ibt card. The Committee on Publication desires to sar that the order in which psperi ire printed in the Publiceliont is decided simply by convenience. In a fcneial Papcrg intencl^ to be prinied in a given number of the Fufficiaiaiii ab'^ould be in the hands of the Commillee not later than [be ar>Ih of the month preceding dale of publication. It is not possible to send proof sheels of papers to be printed to aulhors whose residence is not within ihe United Stales. The respontibllily for Ihe views expressed in the papers printed, and (or Ihe form ol (heir eipreasion. retia vilh Ibe wrilera, and is not uiumed by ibe Sociely itself. The titles of paperi (or reading should be communicaled to eiiher of the Sec- veil a of Ihe itable stamps. The sendings are al the risk of the member. Those members who propose lo attend the meetin(a at Mount Hamilton during the summer should communicate wilh "The Secitury Astronomiol Society of the Pacific," Sludenli' Obiervstory. Berkeley, Cal., in order Ibal ariangemcni! may PVBLICATWSS IS'iVED B! MOf^THLY PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XIX. San Francisco, California, December 10, 1907. No. 117. PLANETARY PHENOMENA FOR JANUARY AND FEBRUARY, 1908. By Malcolm McNeill. I'HASES OF THE MOON, PACIFIC TIME. New Moon Jan. 3, i^ 43m p.m. First Quarter. . . *' 10, 5 53 a.m. Full Moon " 18, 5 Z7 am- Last Quarter *' 26, 7 i a.m Xcw Moon Feb. 2, 12'* 36*" a.m First Quarter.. . " 8, 8 27 p.m. Full Moon " 17, I 5 a.m. I-ast Quarter. . . "24. 7 24 p.m. The first of the three solar eclipses of the year will occur on January 3(1. It will be a total eclipse, the line of totality running through the Pacific Ocean from a point north of Australia to the east coast of Central America. It will be seen as a partial eclipse from points in the central and south- em parts of the United States late in the afternoon. The path of totality is mainly over tiie open ocean, but it crosses several of the small islands in the South Pacific, which aflPord fairly good observing stations. Some of these will be made use of by observing parties from the Lick and other observa- tories. The maximum duration of totality is a little more than four minutes : this is rather more than the average duration. One circumstance is perhaps worth noting. As the line of the eclipse track crosses the line **where the day begins/* the local time of beginning is sunrise of January 4th, and the local time of ending is sunset on January 3d. The Earth is in perihelion on the morning of January 2(\. Mercury is a morning star at the beginning of the year, too near the Sun for naked-eye observations, as it rises only half an hour before sunrise. It passes superior conjunction on the evening of January 13th, reaches greatest east elongation on February 13th, and comes to inferior conjunction on F'ebruary 256 Publications of the 28th. At the time of greatest elongation it remains above the horizon rather more than an hour and a half after sunset, and it will be an easy object for naked-eye view on a clear evening during the late twilight. The interval between the setting of the Sun and of the planet is more than an hour dur- ing the period from two weeks before to about one week after the date of greatest elongation. The duration of visibility and maximum elongation from the Sun are both much less than the average for winter east elongations, for the reason that the planet passes its perihelion less than a day after the time of greatest elongation. There will be a much better opportunity for seeing the planet in June. J^euus is an evening star, gradually increasing its distance from the Sun from 29°, on January ist, to 36°, on February 29th. On the first-named date it sets a trifle more than two hours after sunset, and this interval increases to more than three hours by the end of February. On the evening of February 13th it will be within one degree of the point in the sky known as the vernal equinox. It passes Saturn about noon on February loth, a little more than one degree, or two apparent diameters of the Moon, north of the latter. Mars will not be in good position for observation through- out the year on account of its distance from us and consequent faintness, although it will not be difficult to see it except for a month or two about the middle of the year, while it is near conjunction with the Sun. On January ist it is an evening star, and remains above the horizon until nearly 11 o'clock, atid by the end of l^^bruary it sets a little before 10^ 30"'-. During the two-months period it moves about 38° eastward and 17° nortliward through the constellation Pisces into Aries, ])assing a little north of the vernal equinox on January loth. On January ist its distance from the Sun will be 127 millions of miles. This is more than three times as great as the distance at the time of opposition in July, 1907, and its bright- ness will be not one tenth as great as it was then ; but it will still be as brij^ht as all but the brightest stars, and there is no star as bright in near proximity to the planet, although it is (luitc close to Saturn on January ist. So there will be no difficulty in identifying it. Its distance from the Earth is increasing rapidly, and it will lose more than half its bright- ness by the end of February. Astronomical Society of the Pacific. 257 Jupiter is in fine position for observation, as it comes to opposition with the Sun on January 29th. It will then be above the horizon throughout the whole night, and during the whole two-months period it will be in sight whenever the twilight is sufficiently dark to show it. It is in the constella- tion Cancer, not very near any bright star, and retrogrades, moves westward, about 10°, and 2° northward by February 29th. Saturn is an evening star, setting a little after 10^ 30™ on January ist, and a little after 7^ on February 29th. At the beginning of January it is near Mars, about 2° south, but its slower motion among the stars makes the distance between the planets increase rapidly, and by the end of February it is more than 30°. The very interesting series of appearances and disappearances of the rings which has been going on during 1907 ceases early in January. On January ist the Earth and Sun are on opposite sides of the plane of the rings, but in a few days the Earth passes to the other side of the plane, and for the following fourteen or fifteen years Earth and Sun will both be on the southern side. For some months the rings will present the appearance of a very narrow streak, but in the summer of 1908 the apparent minor axis will be about one eighth of the major. Uranus is in conjunction with the Sun on January 4th and becomes a morning star, but does not get far enough away for visibility until after the end of the period. It is so faint — just within the limit of naked-eye visibility — ^that it cannot be seen without a telescope at a much lower altitude than 25°. Neptune is in opposition with the Sun on January 4th, and is therefore above the horizon throughout the whole night at that time, but it is too faint for naked-eye observation. It is in the constellation Gemini. Jitcahons of the Astronomical ooctety, , iffc. 1 4 NOTICES TO MEMBERS. The next number of our Publications is to contain the new membership list. The Committee on Publi- cation requests the members to notify the Secretary of any changes of address from those given in Publi- cations No. 112. :s! * * The library has at its disposal a fund made up of contributions sent in response to the Society's circular letter asking for help in building up a new library. This money is to be expended for the purchase of books of a popular nature. In order that we may get such books as the members of the Society desire, the Librarian hereby requests them to send to him suggestive lists of books. The only books of a popular nature at present in our library are :— Clerke. Problems in Astrophysics. Clerke. The System of the Stars. HOVESTADT. Jena Glass. Howe. Elements of Descriptive Astronomy. HUGGINS. The Royal Society. Irving. How to Know the Starry Heavens. Langley. The New Astronomy. Webb. Celestial Objects for Common Telcscopcj Young. General Astronomy. pular I NOTES FROM PACIFIC COAST OBSER\'ATORIES. Oriut of the Spkctroscopic Binary 0 DrjICO.ms^ The binary nature of this star was discovered by Director Camprell and announced in iSgg. In the interval from March, 1898, to July, 1904. thirty-two plates were secured that cotiid be used to measure the radial velocity of the star. These were all measured by the writer at Mt. Hamilton, and from the results preliminary elements were computed graphically hj- the fonmUs of LEiiMAXN-FiLHits. These elements were corrected differentially by a least -squares solution which gave the following set of final elements: — Period — 3.0708 ± 0.000032 days f = 0.0141 ± 0.0166 T — J. D. 24i5368.9f^i2 ± 0.499 "^^y^ «,= 126". 112 ± 5S°.6 k = 23.47 :t 0.324 Velocity of system =: — 8.36^'" ± 0.30'"" a sin t — 9.900.000'"". Santiago. Chile, June igo?. Hkber D. Curtis. The Orbits of the Spectroscopic Binaries a C.-iri.\^. kVbLORUM. A-SD a. P AVON is. The binary character of a Carina- and k reloruiii was de- tected by Professor W, H. Wright in the course of (he work □f the D. O. Mills Expedition to the Southern Hemisphere. The binary character of aPavouls was also suspected by him from preliminary measures of the first four plates taken, and was independently discovered from the definitive reductions of the same plates by Dr. S. Albrecht, The three stars are of the same general spectral type described as Type B 3 A in the Harvard classification. In Publications of the ^^^^^* till- pan of ihe spettrimi covered by the spectroscope of Mills rcllector, only six lines are measurable. It is the f ion of the writer that the application of the method of squares to stars of this type of spectrum and number of is not warranted except in the case that a large numbe observations are available, extending over a long interv; time. Preliminary elements were therefore first derived gr ically by the formulfe of Lehmann-Filiies, Changes then made in the derived elements, after comparing wit^ curve given by the observations, and several sets of elen tested by the observation values. With some experienc this method it is possible in a relatively short time to test change the elements given by the graphical solution unti resulting values would be little if any bettered by a 1 squares solution. By such methods the following sets of elements derived : — a Carina. KlV/orMHl. a Pavo« Perioci — 6.744 days ii6.6sday.s ii.-534, H, L. Rice, formerly assistant astronomer at the observatory', has been appointed to the professorship vacated by this retire- ment, and H. R, Mhrg-an succeeds Mr. Rice in the position of assistant astronomer. The organization of the work of the observatory has been changed in the direction of the con- solidation of the work, and Professor W. S. EiCHELBERf.EK. U. S, N., has been placed in charge of all the astronomical work of the observatory. The Committee of the French Academy of Sciences having scientific control of the French geodetic operations on the equator has reported the completion of the rem easu lament of the historic arc in Peru. M. Maurice Loewv, director of the Paris Obser\'atorj', bom in \'ienna in 1833. died on October 15th. while attending a meeting of the national board of French observatories of the Ministry of Public Instruction. Dr. R.\!-Pii H. Ci'HTiss. formerly of the Lick and more recently of the Allegheny Observatory, has been appointed assistant professor of astrophysics in the University of Michigan. Asa['lt Ho//.— The death is announced of .Asaph Hai.l. professor of mathematics U. S. N. (retired). Professor Hall was bom at Goshen, Conn., October 15, iSaq. The early years of his manhood were devoted to teaching school, and it was ' not until he had reached the mature age of twenty-eight years that his astronomical career was begun as student and assistant at Harvard College Observatory. He entered the Naval Observatory in 1862. and remained in continuous con- nection with tliat institution until his retirement in 1891. Professor Hall had the use of the 26-inch refractor at the Naval Observatory, which, at the time it was completed, was the largest refractor in the world. His attention was given chiefly to the measurement of double stars and the satellites of the solar system. Professor Hall also investigated the orbits of several of the satellites, but his name will be longest remembered as the dijcoverer of the two tiny moons of Mars. Astronomical Society of the Pacific. 265 Dr. Elis Stromgren, Privatdozent in the University of Kiel, has been appointed professor and Director of the observa- tory in Copenhagen, in the place of Professor T. N. Thiele, who has retired. NEW PUBLICATIONS. 1 CooKSON, Bryan. Detemiination of the elements of the orbits of Jupiter s satellites from photographs taken at the Cape in 1902. Edinburgh. 1907. 4to;i22pp. Paper. 3s. DuNER, N. C. Ueber die Rotation der Sonne^ zweite Abhand- lungen. Upsala : Akademische Buchhandlung. 1907. 4to; 64 pp. Paper. Hedrick. H. B. Catalogue of zodiacal stars for 1900 and 1920 reduced to an absolute system. Astronomical papers pre- pared for the use of the American Ephemeris and Nau- tical Almanac, Vol. VIII, Part III. Washington: Bureau of Equipment, Navy Department. 1905. 4to; 190 pp. Paper. Kamenskij et E. Korolikov. Les elements approches et Tephemeride de la comete d'Encke. Bulletin de TAcade- mie Imperiale des Sciences. St. Petersburg. 1907. Large 8vo ; 8 pp. Paper. A catalogue of 420 standard stars mostly between 31° and 41° south declination for the equinox 1905.0, from observa- tions made at the Perth Observatory, Western Australia, under the direction of W. Ernest Cooke. Perth. 1907. 4to; 13 pp. Cloth. Astronomical and magnetical and meteorological observations made at the Royal Observatory, Greenwich, in the year 1905. Edinburgh. 1907. 4to. Cloth. Etude de I'atmosphere. Observatoire Constantin. Fascicule II. St. Petersburg. 1906. 4to ; ix + 45 + 92 pp. Paper. 266 Publications of the MiXUTES OF THE MEETING OF THE BOARD OF DIRECTORS, HeLO IN Room 6oi, Merchants Exchange, San Francisco, Cal., on November 30, 1907, at 2 p. m. The following directors were present: Burckhalter, Crawford, Gushing, Richardson, Townley, Ziel. Directors Aitken, Babcock, Campbell, and Hale were represented by proxies. President Cushing presided. The minutes of the meeting of Sep- tember 14, 1907, were changed by substituting "corresponding institu- tions" for "corresponding members," and then approved. The Bruce Medal for 1907 was awarded. The following were elected to membership : — Dr. Thos. Porter, iiii Washington Street, Oakland, Cal. (tem- porary address). Mr. Morgan Sanders, 1419 West Lanvale Street, Baltimore, Md. The following was elected an institutional member: — Public Library, Seattle, Wash. It was moved, seconded, and carried, that the temporary publicatior address of the Society be 601 Merchants Exchange, San Francisco, Cal The Librarian reported briefly upon the present state of the Librarj' Adjourned. Minutes of the Meeting of the Society, Held in Room 601, Merchants Exchange, Sax Francisco, Cal., on November 30, 1907, at 2:30 p. m. President Gushing presided. Upon calling the Society to order he announced that the meeting would be devoted to informal discussion oi current astronomical problems. Professor Leuschner gave a brief history and an account of the present state of the work on the Watson asteroids, which has been car- ried on at Berkeley for the last seven years. Professor Townley made a few remarks on astronomical work at Stanford University, and also gave a brief account of the more recent work on the variation of latitude. Mr. BiRCKiiALTKR Called attention to some recent observations of an unusual cliaracter that he had made upon the rings of Saturn. A general discussion was had upon Professor Lowell's article on Mars in tlie December ( 1907) Century. Adjourned. ftbnomical Society of the Pacific. OFFICERS OF' THB SOCIETY. Mr. Ch*i. S, CusHtHS Priiidinl Ht, A. H. Bilcoci Firil ViciPrtiUtnl Mr. W. W. Cahfbell Stceni VictPrtndml Mr. Gro E, Hm-i Third yiciPrriidtnl Ur. R. T, CM*WFO«n ISlndenW ObserMlorr, Berkeler) Stcrelary Mr, R. G. AtiKIK (Mount Hunilton, 00.) Sicniary Mr. F. R. Zin. Trnnrir flajrd of Directori—iSaui. Anxin, Babcock. Busckhaitei, CAMr»ELt, Ckockii, CuwrOID, CUIHIHC. Hai.1, BlCHASnSON. TDWW.EV, Zm. FiiBHCr Commiltet — Muiri. Ricuaipion, C«ock«, Buickhalteii. Comm^ir^t sn Pn6IiVrifi*oB— Messri. Aiikcn, Towkuiy. M*db»ill. L»fBr> CoinmAfK— Menri. Ci.wrono. Ihviho, Towhibv. Commitlti en Iht Cantet-Mrdal — Mnm. Caupbell (»-amcit>). Bu>r:Ka>i.TEB. NOTICE. The itwntion of new mcmbci. j« c»lled In Arlicle VllI of [he By.Liwi, which calendar year. Thii nie ii necc^ary in order to make our baokkKpinR as limale » poiiible. Duel sent by mail ihould be directed to Astronomical Society of the Pacific. Sludentj' Obser»atory, Berkeler. I( is inlrnded that e»ch mcroher of the Socieir ghill receive a cany of each one af Ibe PHb'icaliani for the year in vhich he was elected to memberEfaip and for ill Bubiequent yean. If Ihere have been (unfortunately) any omiuioni in Ihia oatter, it ii requeated that the Secretaries be at once notified, in order that the auBting numbers may be cupfilled. Members are requested to preserve tbe copic* af the Publicathni of the Sociriy ai tmi to ihim. Once each year a lille-page »nd cententl of the precedint numbera will alio he >ent to the nemheri, who can then . alio be lupplied. to members only, so far as the slock in hand ia sufficient, on the iwrinenl of two dollars per volume to either of the Secreuriei. Any nDa-rstident (nember within the United Slalel Mn obtain books from the Society'a library by aeodinc hi) librarr e*rJ with len cents in itampa to the Secretary A. S. P., students' utaetvalory, Berkeley, Cal., who will return the book and the card. The Camniillee on Publication desires to say that the order in which papers , m printed in Ihe PublKUians is decided simply bf convenience. In i ||ener*l Papers intended lo be printed in a ■iveit"'num^r of 'the PoUicaliotis should be in Ihe hands of the Committee not later than the loth of the montb precedini date tulhor* whose residence it not within the United Sutea, The rupontibili^ for Iha with Ihe writers, and is not assumed by the Society itself. The titles of papers for readini should be communicated to either of the Sec- reurirs as early n possible, as well us any changes in addresses. The Secre- ttrr in Berkeley will «nd lo any memher of the Society suitable stationery, Uaraped with the aeal of the Society, at cost price, as follows; a block of letter paper, ao cents; of note paper, is cents; a paciUBe of envelopes, sj cents. These pticn include postaie, and abould be remitted fay money-order or in U. S. postage Those members who propose to attend the meelinis *t Mount Hamilton durini the Bsmmer should communicate with "The Secretary Aslronomical Society ol the Pacific." Students' ObMrv.tory. 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The Astronomical Society of the Pacific. LORD KELVIN. By H. C. Plummer, The death of Lord Kelvin, which occurred in the closing J days of the past year, concerns primarily that science the progress of which he did so much to mould, but also, scarcely less degree, all those sciences which are largely de- pendent on the development of the fundamental principles of natural philosophy, and among these not least astronomy. A dominant figure among men of science throughout the latter half of the nineteenth century, and, since the death of . V. Helmholtz, in 1894. beyond dispute the greatest living j physicist, he has passed away in the full fruition of his genius at the venerable age of eighty-three years. Those who had the privilege of listening to him so lately as last August at the Leicester meeting of the British Association will not easily forget his inspiring example or how perfectly his mental pow- ers were maintained to the end of his long life. Indeed, the mature power manifested in his early youth, the youthful enthusiasm of his old age, and the life of unwearied achieve- ment which lay between, are alike remarkable in a brilliant career. WiL[.i.\M Thomson was born at Belfast in June, 1824. His father, at that time professor of mathematics in the Bel- fast Acailemical Institution, was called, eight years later, to fill the chair of mathematics in Glasgow University. This was the beginning of that long and memorable association with the ancient Scottish seat of learning which enabled Lord Kelvin to say truly, on the occasion of hia installation as Chancellor three years ago: "I am a child of the University of Glasgow. I lived in it sixty-seven years (18^2 to 1899)." In the same address he has drawn a fascinating picture of the university in the thirties, and of his own early studies there. His precocious abilities were tndy astonishing, and there can be no doubt but that he had the good fortune to be placed in an environment which fostered them to the utmost. He was matriculated in 1834. at the age of ten, and studied Latin under William Ramsay. Greek under Sir Daniel Sandford and Llsiiington, logic under Robert Buchanan, and moral philosophy under William Fleming. From his father he learnt'd matiiematics and much else besides, from William CouPKR zof)!ogy and geology, and from Thomas Thomson chemistry. The latter, "a very advanced teacher and investi- gator," had already realized a well-equipped laboratory, which preceded Liedig's famous laboratory at Giessen. As regards his indebtedness to his teachers in natural philosophy, Lord Kelvin's own tribute may be quoted: "My predecessor in the natural philosophy chair. Dr. Mejklkham, taught his students reverence for the great French mathematicians, Lf.gendre. Lagrange, Laplace. His immediate successor in the teaching of the natural philosophy class. Dr. Nichol, added Frks.vel and Fourier to this list of scientific nobles; and by his own inspiring enthusiasm for the great French school of mathematical physics, continually manifested in his experimental and theoretical teaching of tile wave theory of light and of practical astronomy, he largely promoted scien- tific study and thorough appreciation of science in the Uni- versity of Glasgow." The youthful student made splendid use of splendid opportunities; he repaid them by lifelong devoted service and added luster to an illustrious foundation. The years that followed at Cambridge seem only an inci- dent in the career of one who had already read something of the "Theorie analytique de la Chaleur" before his sixteenth birthday. William Thomson was second wrangler in the tripos of 1845, and first Smith's Prizeman in the same year. He was immediately elected to a fellowship at his own college. Peterhoiise, but he was not destined to remain at Cambridge. In the following year, after working for a time at Paris, in the laboratory of Regnault at the College de France, he was elected, at the age of twenty-two. to succeed Dr. Meikleham in the chair of natural philosophy at Glasgow. This office he filled continuously for fifty-three years, until his resignation Space forbids a detailed reference to the brilliant and many- sided work of original discovery which Lord Kelvin crowded into this memorable period of scientific history. Much is matter of common knowledge; many excellent notices have been published since his death, and it is understood that an authentic biography by Professor Silvanus Thomp.son is to appear shortly. Even if the view is restricted to the astro- nomical standpoint, and an attempt is made to appraise the /Istrottomicai aoctety of tne factpc. \ 5 debt which astronomy owes to Lord Kelvin's work, the points of direct contact and of indirect inflnence are so manifold that they enforce his own dictum, that all science is one science and that any part of science which places itself outside the pale of the other sciences ceases for the time being to be a science. Thus he served the cause of submarine telegraphy alike by the theoretical discussion of the conditions of the problem, by the invention of practical receiving apparatus, and by his indom- itable scientific faith al a time when Aihv declared an Adantic cable to be on mechanical and electrical grounds impossible : and while the realization of the cable is a benefit to humanity at large, the astronomer incidentally owes to it the fact that the ocean has been no longer a barrier to accurate determina- tions of longilnde. The mirror galvanometer, again, which constituted his earhcr form of receiving apparatus, has found innumerable applications; perhaps its most direct service to astronomy is to be seen in La.vglev's use of it as an essential part of his l>olometer. These examples are quoted merely to show that there is scarcely any part of Lord Kelvin's activity which is not of interest to the astronomer. His researches covered the whole field of electricity and magnetism, ranging from developments in the subject of electrostatics, with the beautiful theory of images, to the invention of numerous in- struments for precise measurement, used in every physical laboratory and by every electrical engineer, and so perfectly designed as to remain nnchanged even in detail. For work in the theory of heat Lord Kklvin was particu- larly well fitted by his early training and by his association. brief though it was, with Regnaui-t. He was also fortunate in the friendship and co-operation of Joule. In this field some of his best and most original work was done, both on the theoretical and the experimental aide. By his restatement of the second law of thermodynamics, by his definition of an absolute thermodynamic scale of temperature, and by his discovery of the principle of the dissipation of energj-. he is entitled, along with Clausius, to rank as one of the founders of thermodynamics. On the experimental side his best work was the "porous-plug experiment" carried out in conjunction with Joule, and his researches in thermo-electricity, includ- ing the discovery of the "Thomson effect." By applying the analysis of Fourier to the consideration of the thermal con- Publications of the dilion of the Earth, Lord Kelvin was led I famous limit to its possible age as a habitable j brought about the celebrated conflict with the uni formitarians. and has exercised a profound influence on the thoughts of geologists. The opposing views were never entirely reconciled, and the question at issue has been reopened by the recent discovery of sub-atomic sources of energy. The same ques- tion is also involved to some extent in Sir George Darwin's theory of the evolution of the Earth-Moon system. The problem of the age of the Earth is only one aspect of that presented by the mechanical energies of the solar system which in al! its generality occupied Lord Kelvin's attention from an early date. He first examined the theory that the heat of the Sun was maintained by the influx of meteoric mat- ter from outer space, and rejected it after a careful quantitative estimate on the ground that the number of meteors required to supply the loss of heat by solar radiation is enormously in excess of what is compatible with terrestrial experience. He then adopted the suggestion of v. Helmholtz. that the energy emitted in a radiant form was gained by the contraction of the Sun's mass at the expense of gravitative potential energy. This doctrine, to which Homer Lane contributed in this country, led him to investigate the conditions of a spherical mass of gas in convective equilibrium. There are many obsta- cles in the way of adapting this theory to actual stellar condi- tions, and the difficulty of drawing definite conclusions has not been diminished by the new possibilities presented by the energy set free in radio-active transformations; but of the suggestive importance of the theory there can be no doubt. Many investigations were made by Lord Kelvin in the region of hydrodynamics, and his work on tides is of great importance. To him and to Sir George Darwin is due the fact that tidal theory is now practically perfect. The part which he took in devising mechanical means for calculating tides resulted in a practical labor-saving machine for predicting the tides of the Indian Ocean. He also designed a tide recorder and a harmonic analyzer. Graphical and mechanical methods of performing calculations, and in particular of solv- ing differential equations, possessed much interest for him. and it may be noted that the method of mechanical quadratures employed by Sir George Darwin in his memoir on Periodic r Astronomicat Society of the Pacific, 17 Orbits is the numerical counterpart of a graphical method described by Lord Kelvin. Of great interest to the astron- omer are his researches regarding the pliysical condition of the Earth, in which, by masterly use of the results of tidal observa- tions and of the theory of nutation, he arrived at definite conclusions as to the rigidity of the external and internal substance of the Earth. The stimulus derived from personal intercourse with Professor Newcomb ied him farther to exam- ine the possible variation in the diurnal period and axis of rotation, some fifteen years before the accurate observations* of Professor Kustner and the comprehensive discussions of Dr. Chandler had revealed the true nature of the problem of the variation of latitude. I-ord Kelvin was himself a keen yachtsman, and to the art of navigation he has rendered immense services by applying his inventive genius to its needs. By observing true scientific principles he invented and manufactured the standard type of mariner's compass. His apparatus for sounding by means of piano forte- wire is as simple as it is effective. As regards the astronomical .'^ide of the seaman's art, he advocated the use of Sum.vek's method for finding a ship's place at sea, and ptiblished tables to facilitate its application. Here it may be re- called that he wrote several papers on chronometers and clocks, including electrical controls, especially an important one in which he discussed the effect on the rate of the form of suspension. One contribution he made to purely practical astronomy: this was a photometric study of the Sim and Moon and a comparison of their light with terrestrial standards. In conjunction with the late Professor Tait, Lord Kelvin wrote the classic "Treatise on Natural Philosophy." which was translated by v. Hei.mholtz, and has been used as a text-book perhaps even more extensively in Germany than in England. The resjionsibility for the abbreviated title, "T and T' " has been variously assigned. The breadth of view and the stimu- lating interest of these two volumes must cause a regret that a scheme so brilliantly begim was not carried farther. But it is matter for satisfaction that Lord Kelvin lived to amplify and to publish his "Baltimore Lectures" twenty years after the date of their delivery (in 18841 at the Johns Hopkins Uni- versity. Here are to be found in a collected form the final results of his researches in molecular dynamics and the wave Publications of the theory of light, more particularly concerning the dynamical theory of dispersion. Of late years much of his thought was devoted to the ultimate structure of matter and the true nature of the lether. It would be idle to pretend that his views on these matters towards the end of his life gained very general assent. The I which he persistently retained in the word "electrion" seemed symbolical of a certain divergence on his part from the main stream of contemporary thought. And indeed his death significantly marks an epoch in scientific history. The school of which he was so brilliant an example was not content with anything less than a complete dynamical explanation of phenomena. This phase of scientific positivism is passing away, and the tendency since the publication of Clerk Max- well's electromagnetic theory has been unmistakably, if per- haps too hastily, more and more in the direction of "aether and no matter," to quote Professor Lamb's parody of the title of Professor Larmoh's book. Yet, if the whole of Lord Kelvin's ideas are not destined to find acceptance, his possible weakness is closely allied to the great source of his strength, his passion for the concrete. The man who makes no mistake makes nothing, and no man ever more ruthlessly destroyed the creatures of his own fertile brain, when he deemed them to have become erroneous or useless, than Lord Kelvin. Of him v. Helmholtz wrote thirty years ago: ". , . be has done very much to destroy the old unnat- ural separation between experimental and mathematical physics, and to reduce the latter to a precise and pure expres- sion of the laws of phenomena. He is an eminent mathema- tician, but the gift to translate real facts into mathematical equations, and rice versa, is by far more rare than that to find the solution of a given mathematical problem, and in this direction Sir William Thomson is most eminent and orig- inal." It has been denied that he is to be regarded as a mathematician in the strict sen.se. It is true, perhaps, that in his own branch he was not the equal in this respect of v. Helmholtz himself, or of Stokes, to mention no others: but the complete denial of his claim rests upon the restriction of the word "mathematics" to the pure variety. As a logical dis- tinction this may be harmless enough, but if the idea is extended in the region of education to the practical separation of the pure and applied branches the result is likely to be unforl Astronomical Society of the Pacific. for both. There is Httle doubt that without the due co- operation of the two the Cambridge school of mathematical physicists would have been shorn of its chief glories. Lord Kelvin had traveled widely and had made several visits to this country. The last was in 1902, when he received a generous and enthusiastic welcome, which will be within the memory. Some of the impressions which he received during a visit in 1876 are recorded in his presidential address to Section A of the British Association in the same year, and some of his words on that occasion may be of interest: — "... I wished to write an address of which science in Amer- ica should be the subject. I came home, indeed, vividly im- pressed with much that I had seen, both in the great exhibition of Philadelphia and out of it, showing the truest scientific spirit and devotion, the originality, the inventiveness, the patient persevering thoroughness of work, the appreciativeness. and the generous open-mi ndedness and sympathy, from which the great things of science come. . . . "I wish I could speak to you of the veteran Henry, generous rival of Faraijay in electromagnetic discovery; of Peirce, the founder of high mathematics in America; of Bache, and of the splendid heritage he has left to America and to the world in the United States Coast Survey ; of the great school of astronomers which followed. Gduld, Newton, Newco-mb, Watson, Young, Alvan Clarke, Rutherford. Draper, father and son ;" nor does the passage end here. Only those who have heard Lord Kelvin speak will be able to realize the glow of enthusiastic sincerity with which such a tribute would be uttered. Many years ago it was said that "in Sir William Thomson the most brilliant genius of the investigator is associated with the most lovable qualities of the man. His single-minded enthusiasm for the promotion of knowledge, his wealth of kindliness for yoimger men and fellow-workers, and his splen- did modesty, are among the qualities for which those who know him best admire him most." These qualities were only enhanced with advancing years. Withal, he was endowed with the shrewd business capacity of his race, and not only per- sonally supervised the manufacture of his numerous patents but also acted as a director of several public companies. He was conservative to the core — and that not merely in the Publications of the- ix>litica1 sense. This 13 to be seen in his strict adherence to Newton's formal enunciation of the principles of dynamics, though liis colleague Tait was more outspoken in his denun- ciation of any departure from the Newtonian position. The advocates of the retention of compulsory Greek in the ancient universities were also able to quote in their favor an opinion bearing all the weight of [x)rd Kelvin's authority, and, it may be added, in the light of his early training, of his personal experience. Great and varied were his talents, and worthily he used them for the benefit of mankind. .\\\ the successes, all the honors, that could fall to the lot of a man of science were his. He was president of the British Association in 1881, and in succession to Sir Geohge Stokes was president of the Royal Society from i&jo to 1895. Nowhere will his presence t)c more keenly missed than at the annual meetings of the British Association, which he attended so assiduously. His con- nection with his own University of Glasgow was crowned by his election as Chancellor in 1904. On his return from the laying of the first successful Atlantic cable, in 1866. his services to the state were rewarded with a knighthood; later, in 1892, he was raised to the peerage under the title of Baron Kelvin of Largs. When the Order of Merit was instituted by King Edward, in 1902, he was chosen as one of the first members of that select band. Other decorations. British and foreign, were showered upon him. The learned societies of his own and other countries had done him such honor as lay within their power. And the last solemn distinction which Eng;^land has to bestow was reserved for him. Amid a scene which the December gloom of a London day served only to render the more impressive, in the presence not only of representa- tives of the King, of foreign governments, of the whole world of learning, but . also of vast numbers who must have felt a deep sense of personal loss, he was laid to rest in Westminster Abbey. There he finds a place in close proximity to him whom he would be the first to acknowledge as his master. Isaac Newton. His fame is secure in the comprehensive influence which he exercised on the scientific progress of his generatiw his is the "monuineninm (rre perennius." Astronomical Society of the Pacific, 21 ASTRONOMICAL OBSERVATIONS IN 1907. Made by Torvald Kohl, at Odder, Denmark. Jan. V.xRiABLE Stars. (The instrument used is a 3-inch Steinheil, power 42.) S Urs(€ Majoris.^ = i. Feb. Mar. Apr. May Tiilv Aug. 4 8 II 16 5 24 3 10 19 23 II 6 16 5 21 I { f. id. id. 2 steps > g. = h. I step < h. >g- ■ f. id. 1 step < e. 3 steos > d. 2 steps > d. = e. f. Aug. 26: Sept. 30: 4: 8; in 12: 15: 17: 24: 28: Oct. 5: 12: Nov. 25: 13- 29: Dec. 29: id. gr- id. id. id. I step > g. = S- = h. id. invisible. id. I step > f. ( in the midst 1 between d and e. 1 N'ide the sketch in the Publications A. S. P.. No. 73, p. 56. Jan. 4: T invisible. 8: id. it: id. Feb. 16: a. May II : a. July 6 : I step < e. 16: id. T Ursa Majoris.^ ' Aug. Sept. Oct. .=; 26 30 4 8 II 12 i.S 17 2A. 28 5 12 25 Nov. 13 29 Dec. 2Q I step < f. very faint. id. id. id. id. id. id. id. invisible. id. id. 3 steps < f. r>f- I d. 3 steps > a. 5 steps > a. * Vide the sketch in the Publications A. S. P., No. 22. p. 63. 22 Publications of the W Pegasi,' Jan. 4 ; W = b. Oct. 6: ii: id. 12: Feb. i6: J d. Nov. 25: 5: Aug. 26: utmost faint. 30 ; I step < g. 13: 26: ■l e. = d. in the midst between d and c. in the midst between c and b. b (3) W (2) c. * Vide the sketch in the Publications A. S. P.. No. 60p p. 23. SS Cygni} Jan. 4, 7": SS g. Sept. 30, 1 1" : < g. 8, 8": id. Oct. 5, lo"" : I step < g II. e^: = c. 6, 8": id. Sept. 4, 9j.: I step < g. 12, 8'': id. 10, 13. 9": id. .5, 8-|>- 24. 8'': invisible. Nov. 29, 6*> : < g. 26. 8'': b. II : I step > b. Mar. 5: — b. Apr. 3 : id. Apr. 19: -A. Aug. 21 : I step > A. Oct. 5- -A. Nov. 29: id. Dec. 29: id. As comparison-stars I have used A = B. D. + 20° 1095 (7'".4) and b = B. D. + 20° 1073 (8"*.2). This irregular vari- able star has had its greatest brightness, in the summer of 1907. Meteors. Fireballs have been observed at the following dates: Jan- uary nth, I2th, 14th, February 15th, March 4th, May 14th, July i6th, October 18th, November 6th, 7th, 20th, 26th. De- cember 5th, 25th. .Astronomical Society of the Pacific. 23 Shooting- Stars. Shooting-stars have been observed from eight stations in Denmark and Norway in the period August gth-iith. Only on August nth the weather was favorable. At these stations 170 paths of shooting-stars were mapped, but only three proved suitable for calculation. These three meteors have given the following results: — For Obsenvtioii. Ti>0(. Slilion. B^i„„;„i. Endini. M«. ObKi .11.- 0 Pv / Odder I. 11 4/ 0 P.M. j fjyborg '00° + 55° 148+54 1 +66 .5 249 + 24 .5 2+12 nr + so°-5 * t^"- *■■■ 159+44 1 {/-N 357 +57 2 """ 2^3 +18 a J- F- ^J 356 + a a T. K6 li +33 4 +as I ^"- '' For Calculation. Bendiilum instead of the usual mercury pendulum. This becomes pos- sible through the invention of a combination of nickel and steel, the coefficient of expansion of which is exceedingly small. Tile arrangement for supplying the motive power shows the greatest departure from old lines. Three Edison- La I an dc cells, connected in series and regulated by a rheostat, supply .the power for lifting the driving weight of the clock. This weight, about ten grams, is pivoted at one end, and at the Other engages, with a pawl, a wheel directly connected with what is known as the third wheel in clocks of the ordinary winding devices. When the weight has finished its fall, it completes the battery circuit and is lifted again by an electro- magnetic lever. The relation between the weight lifted and the strength of the battery is such that the intervals between lifts may vary from 28* to 34". If it becomes less than 28", a little falling off in battery strength will result in failure to wind. ■Since it can fall from the highest possible position in 34", any attempt to increase the battery strength t>eyond the amount necessarj- to raise it to this point only produces a violent contact at the top of its lift. A daily note of this interval gives a check on the battery strength and a warning when to lessen tiie resistance in the rheostat. The device works very ■ smoothly. ■ To secure a constant pressure, the entire clock is mounted inside a heavy cylindrical glass case consisting of two parts, the perfect sealing of which is secured by ground-glass sur- faces coated with vaseline. Between December 1, 1906. and the latter half of June, 1907, the clock ran for several short periods under such varying conditions that no results of value could be obtained there- from. The clock was finally started, sealed, and the air pres- sure reduced to 560™", in the latter half of June, 1907. The ™, with i 30 Publications of the mean yearly pressure at Mt. Hamilton is about 650"", a range of ± 13""; so that 560"", being 90"™ less than nor- mal, is safely below any possible outside pressure. At present the clock is mounted in a small fireproof room fitted with double doors, in the basement of the Meridian Circle House. There is no other provision for constant temperature, and therefore the pressure varies within the glass case with variations of temperature. But since the effect of outside temperature is felt only gradually inside the case, the pressure varies in a correspondingly gradual and progressive way. never falling precipitously, as is the case outside just preceding a stonn. All the data gathered since the clock was completely fitted up and started, in June, 1907. has been carefully gone over, giving a full six months' uninterrupted rate. These rates were derived from observations for clock correction with the Meri- dian Circle, either in connection with some current programme or from especially prepared lists. Up to September 4lh, Dent sidereal clock, numbered No. 4 in our series, was used for a standard, with which all the other sidereal as well as mean- time clocks were compared daily. During this period the rates derived for No. 5, the Riefler, were frcMH corrections of either the same or but slightly later ejKichs. After September 4th, owing to an unsatisfactory fluctuation in the rate of No, 4, No. 5 was substituted, so that during the rest of the period its rates are derived directly from observations. Clock errors during the six months from June, 1907. to January. 1908, were derived from observations on an average of every six days, and, except for one interval of seventeen days, were quite uniformly distributed. During the same interval the average temperature was 54''.8 F., with an average range of 3° for the intervals be- tween which clock corrections were derived. The maximum for the period was + 64° F., in August, 1907, and the mini- mum + 42° F., in December, 1907. It would have been bet- ter, had a whole year of observations been available, for at present data can be used only during a period from maximum to minimum temperature. A complete year would also have given the reverse condition as temperature went from min- imum to maximum again. During December, 1906, when the clock was first started, the thermometer went as low as Astronomical Society of the Pacific. 31 I -\- 35° F., giving a range of 29° for the year against 22° I for the six months used. At that time, however, the clock was exposed more than usual, while being adjusted, and tem- peratures outside were unusually low. also. A plot of the rate during ihis period, together with a plot of temperature and barometer range during the same period, show quite exact agreement. Whether this rate change is due directly to temperature effect on the pendulum, or indi- rectly through its effect on pressure, or to both, is as yet uncertain. It would be possible to test the direct effect of temperature, if the pressure were watched carefully, and kept constant by admitting more air or pumping out, as circum- stances required. However.it is possible to arrive at the variation in clock rate and barometric change concurrent with temperature variations. Readings of the thermometer are made to the nearest degree and of the barometer to the nearest millimeter. A least-square solution of the data gives -f 1.3""° as the change in barometer per degree Fahrenheit. This, when applied to the barometric readings, gives an average residual of ± 0.73™'", which is about one ninth of the average residual for uncorrected read- ings of the barometer. Charles's law states that the pressure of a gas. of constant volume, varies directly as the absolute temperature. .\\. the pressure here considered the variation of pressure per degree I-"ahrenheit amounts theoretically to -|- 1.1°"". This, taken in connection with an observed change of -f- 1.3"'" per degree Fahrenheit, shows that the sealing of the glass chamber is quite satisfactory. The average rate for No. 5 for the period was — o'.i65 per day. with an average residual of ± o'.oSg. The smallest was o*.oo. in August. 1907, at a temperature of -^61". d F,. and the largest — o".37, in December, 1907. at a temperature of + 42^.8 F. From the plot, mentioned before, it was evident that a change of rate accompanied a change of temperature. A least-square solution for this variation gave -(-o'.oi6 per degree Fahrenheit. When the rate is corrected for tempera- ture, the average residual is ± o'.042, as compared with i: tf .089, the average residual for obser\-ed rates. The rates for the two Hohwu sidereal clocks, numbered No. 3 and No. 8 in our series, have been derived from comparisons with the standard sidereal clocks at epochs corresponding to Ptiblicationi of the cxl the residual I those used for the Kiefler. During this period I from the mean rate was more than twice as large as usual, being ± cy.ay and ± o*.32 respectively. A change of rale of r in liiat time was quite apparent in both clocks. When a change of rate of -\-cf,a^ for No. 3 and — o".04 for Na 8 per interval between which clock corrections were obtained, is applied to these rates, the average residuals are reduced to ± o'.i4 in both cases. Previous investigation has failed to connect changes in the rates of these clocks with tem- perature variations, and the fact that in the present instance the changes of rate of the two, wiiile numerically the same. are of opposite signs, leads to the same conclusion. These clocks are mounted in the clock-room, with no particular protection from changes of temperature in the room. Dent sidereal clock, until September 4, 1907, used almost exclusively for a standard upon which to base the others, has been recently investigated by Professor Tucker in connection with some of his fundamental work. He is quoted as fol- lows :— "The Deut clock is inclosed in a small chamber built into the clock-room, and is protected by double doors from changes of tem|>erature in the larger room. The daily change of tem- perature in the clock rarely amounts to more than one degree, and is usually progressive for periods of considerable length. "The total variation in a year averages 34°, from 40° to 77° F. being the extreme range on record. During the periods of about one week, into which the tabulation of corrections is divided, the average change is less than 4°. The maximum falls in August, the minimum in December, and the mean temperatures occur in June and October. The yearly mean is close to 58°. "The variation in the rate of the clock has a well-established connection with the change in temperature, which has gen- erally been reckoned at -f- o'.04 for a rise in temperature of one degree. For a period of seven months, in 11)07. March to September inclusive, the change of + o'.o^ has recently been derived, by least-square solution, The application of this temperature correction to the rate results in reducing the average residual for the weekly intervals from ±if.2\ to ±c^.ii. for the seven months. The clock retained a consist- ent rate during this period, which shows the Dent at perlu I Astronomical Society of the Pacific. 33 D best performance. Preceding and following this period, the Rte of the clock made abnipt changes." t Taking into consideration this somewhat erratic action on F; part of the Dent, and the highly satisfactory way in which ; Riefler has been performing, its arrival was timely. Thanks are due to Professor Tucker for aid in preparing his note. r. f. Sanfobd. Mt. Hamilton, Cal, January 2.1, '<»»- The Eclipse of January 3, 1908. . Before this number of the Publications goes to press, I take i^asure in announcing that the total solar eclipse of January t 1908, was observed successfully by the Crocker Expedition (wn the Lick Observatory, University of California, and by be expedition of the Astrophysical Observatorj', Smithsonian bstitution. The united expetlitions were landed on Flint Uand on December 9th by the U. S. gunboat "Annapolis," in land of His Excellency C. B. T. Moore, U. S. Navy, ivemor of Tutuila. An observing site was selected in the idst of the cocoanut-trees, and preparations proceeded rap- '. notwithstanding the tropical heat and the multitudes of iwcrs. Every arrangement for securing the observations iring totality was completed in good time. The forenoon of January 3d was alternately clear and idy. with the clearness much in excess. About ten min- 'S before the eclipse was total, clouds formed rapidly, until sky was densely covered. Just as the time-keeper called brcun his chronometer. "Five minutes before totality," a Irenching rain fell, and all seemed lost save honor. At the nd of two or three minutes the rainfall began to decrease Bid the clouds in the east gave signs of breaking. Less than a Bnute before totality the slender crescent of the Sun showed lintly through the clouds, though a moderate rain was still lUing. The rain and clouds grew rapidly lighter, and the ist drops fell at two or three seconds after totality began. Mmediately after the beginning of totality the corona was lintly visible through the thin clouds. These continued to bperse rapidly. During the second (|uarter of the total base the clouds were extremely thin, and during the third od fourth quarters the sky was essentially clear. About ten seconds before totality, the rain having nearly ceased, the order was given to the workman seated on top of the outer of the two lowers supporting the forty-foot camera to remove the tarpaulin from over the lens. The order was executed promptly and the remnant of the Sun's crescent was seen by the observer inside of the camera just one second before totality. The signal "Go!" was called by the observer at the instant when the crescent disappeared. Such of the instruments as were still covered, awaiting the end of the rain, — for example, the larger ccelostat. — were uncovered within a few seconds, and the programme of observations was thenceforth carried through without a single slip. The twenty instntments. driven by seven clocks, and the twelve observers did their work to perfection. Two spectrographic exposures planned for the twelve secfmds immediately preceding totality were necessarily omitted, and some of the sensitive plates were damaged by getting wet in the downpour. The remain- ing exposures were expected to give good results; and such proved to be the case when the plates were developed, during the following two nights. All of the instruments were in perfect foctis and adjustment. The observing station of the Smithsonian Institution w^as located on the beach, for scientific reasons, about one fourth of a mile northwest of the Lick Observatory station. Here the rain was lighter and the sky cleared earlier, so that Direc- tor AnBOTT had an essentially clear sky during the whole of totality. His interesting programme was carried out to his complete satisfaction. Immediately following the drying of the photographic negatives, they were packed with care and sealed in tin for shipment to Mt. Hamilton. The expeditions re-embarked on the U. S. gimboat "Annapolis" on January 5th, arrived in Tahiti on the 7th. and in San Francisco on the Z5th. All the members of the expeditions were entirely free from illness at Flint Island. We received extensive assistance from many people, which it will be a pleasure to acknowledge in our first formal publi- cation on the subject. An English expedition, in the charge of F. K. McClean, Esq., was our near and agreeable neighbor from December 23d to January .^d. Mr. McCle.\n's party sailed from Flint ' Astronomical Society of the Pacific. 35 IJsland about three hours after the eclipse occurred, the plan "lieing to develop the photographs in the dark-room on his •rcssel. We hope that his photographs have been found to be Itoccellent. \V. W. Campbell, .' GouiEN Gate, January 25, 1008. iSoME Tests of the Vertical Co^lostat ob "Tower" Tele- ' SCOPE OF THE Mt. Wii.so\ S'olah Orservatohy. I The vertical crelostat telescope described in Contributions Ifrom the Solar Obscn-atory, No, 14, was erected on Mt. Wilson [last summer, and has been in regular use since October. A 17-inch Cftlostat, with mirror 12 inches thick, is mounted at Hk suinmit of a steel tower 05 feet in height. From the crelo- 'stat the sunlight is reflected to a second mirror of elliptical form, which sends it vertically downward to a 12-inch visual objectivt; of fto feet focal length. The solar image is formed in a house at the base of the tower, where it is studied with a spectrograph of 30 feet focal length, standing in an under- ground chamber 8,^ feet in diameter and 30 feet deep. A spectroheliograph, also of 30 feet focal length, is being con- structed for use with this telescope, but at present a simple attachment to the spectrograph adapts it for the monochro- matic photography of the Sun. The 5-foot spectroheliograph, when used with the Snow telescope, yieids excellent photographs of the calcium, hydro- gen, and iron floccuU. For narrower lines, however, higher jdispersion is required, which involves longer exposures. With 'tfie Snow telescope these cannot be given, on account of the .change of figure of the mirrors in sunlight. There is not only a marked lengthening of the focus, but also a decided effect uof astigfmatisni, due to the distortion of the two plane mirrors. I^The mirrors of the vertical ccelostat telescope (commonly Iknown as the "tower" telescope) were made very thick in the hope of reducing this distortion. This plan has succeeded admiralily, though there is reason to believe that even better results would have been obtained if somewhat thinner glass disks had been used for the mirrors. ' The change of focus is so slow that an exposure of half an ations. — Observed times of contact seem to have been about a minute earlier than computed times. The black ligament was conspicuous. TTie planet ap- peared very black. Little evidence was obtained of the pres- ence of its rare atmosphere. Meteorites. — The Journal R. A. A., Volume XVTTI. No. 2, gives notes from an abstract in Xatiirc. by L. J. S., of "Sonic Astronomical Society of the Pacific. 45 Recent Papers 011 Meteorites." Dr. H. A. Ward, in Proceed- ings of the Rochester Academy of Science, Volume IV, pages 137-148, 1904, describes the Willamette meteorite, found in 1902 near Willamette, Oregon. The mass of metallic iron measures ioxfi5'ix4J-^ feet, and weighs about 15,''^ tons, being the third largest meteorite known. The two heavier ones are the Anighito, of 36^ tons, brought by Peary from Greenland, and the Bacubirito (Mexico), with an estimated weight of 2y'/2 tons. The Willamette meteorite is conical in form, and was found embedded in the ground, base uppermost. It is probable that in consequence of weathering none of the original surface remains. .Analysis shows 91.5 per cent of iron. 8 per cent of nickel, and small amounts of cobalt and phosphorous. Professor O. C I'ahkington, in Field Colum- bian Museum Gcol. Ser., Vol. III. pp. 57-110. IQ07, collects 360 published analyses of 248 meteoric irons. The average composition is: Iron, 90; nickel, 9; cobalt, 0.9; copper, 0.02 per cent. \otes from "Science." — The Lalande prize of the Paris Acad- emy has been awarded to Mr. Thomas Lewis, of the Royal Observatory, Greenwich, and secretary of the Royal .Astro- nomical Society. Tlic Observatory states that during the last twenty years there have been twenty-one recipients of this prize, of whom nine were American, nine French, one South American, one Italian, and (the present award) one English- man. Dr. Walter M. Mitchell has been appointed director of the Haverford College Observatory. Pierre Charles Cesar Janssen, director of the Meudon Astrophysical Observatory, died on December 23d, at the age of eighty-three yearfi. M. GoN'N'ESSiAT, of the Paris Observatory, has been ap- pointed director of the Observatory of Algiers. Dr. E. O. LovETT, professor of mathematics at Princeton University from 1900 to 1905, and since professor of astron- omy, has resigned to accept the presidency of the institute established at Houston. Texas, by the late William H. Rice. with an endowment, which, after long litigation, is said still to aitioimt to over two million dollars. M. BiiURGET, of the Toulouse Observatory, has been ap- pointed director of tlie Marseilles Observatory, to succeed M, Stephen, who has retired. M. M. Nyren, of the Pulkova Observatory, retired from his office at the end of 1907. Charles A. young.— On January 3d America lost another of her eminent astronomers through the death of Professor C. A. Young, at Hanover, N. H., to which place he retired after becoming professor emeritus of astronomy at Princeton University in 1905. An appreciative article on the life and work of Professor YouNG was published by Director E. B. Frost, in Science for January 24th, and it was from this article that most of the information given below was obtained. "Chakles Augustus Young was bom on December 15, 1834, at Hanover, where his grandfather and father succes- sively occupied the chair of natural philosophy in Dartmouth College during the period from rSio to 1858. He entered college early, and graduated with distinction in 1853 as bache- lor of arts. During his student days he assisted his father in astronomical observations, and accompanied him in 1853 on a trip to Europe to purchase inslnmients for the Shattuck Observatory, then in the course of erection. For two years after graduation he taught classics at Philips Academy, pur- suing at the same time theological studies at the Andover Seminary. In 1857 he went to Hudson. Ohio, as professor of mathematics and natural philosophy at Western Reserve. During several summer vacations he assisted in the govern- mental survey of the Great Lakes. Responding to the call of patriotism in 1S62, he was for four months captain of Company B in the Eighty-fifth Regiment of Ohio Volunteers, which was largely recruited from students. "In 1866 he returned to Dartmouth as professor of natural philosophy and astronomy, thus continuing the family tradi- tion. ... In 1877 he accepted a call to Princeton, where much larger instrumental facilities were offered to him, with less confining teaching duties. He gave, however, much time to the organization and equipment of the Students' Observatory, making it then probably the best in the country. A powerful spectroscope was provided for the 23-inch equatorial of the Halsted Observatory, and with this he made important observa- tions of the chromosphere and sun-spots." r Astronomical Society of the Pacific. 47 Professor Young was especially interested in the physical side of astronomy, and was one of the pioneers in the use of the spectroscope, especially in its application to the study of the Sun. He ohserved the solar eclipse of 1869 at Burlington, Iowa, and deuionst rated from his observations the g;aseous nature of the corona; that of 1870, in Spain, when the flash spectrum was seen for the first time; that of 1878, at Denver; and that of 1900, in North Carolina. He also made a trip to Russia in 1887 to observe the eclipse of that year, but clouds intervened. In 1873 he spent the summer in Wyoming, ' at an altitude of 8,000 feet, for the purpose of measuring the wave lengths of lines of the solar spectrum, which could not be successfully observed at lower altitudes with the instru- mental equipment then available. In 1874 he observed the transit of Venus at Peking. Professor Young's excellent book, ''The Sitn," first is.siied in 1881, and last revised in 1895, has been translated into several languages. Professor Young's text-books, "General Astronomy," "Manual of Astronomy," "Elements of Astronomy," and "Lessons In Astronomy," constitute the most popular and successful series of text-books on astronomy ever issued, and have been used by over a hundred thousand students. Pro- fessor YouS"G was very successful as a teacher, and belonged ' to that class of men who are the most useful in the American university of to-day,— eminent investigators who are also suc- cessful teachers. S. D. T. Head of Southern Obserz'atory.— The superintendence of the work at the proposed Southern Observatory of the Car- negie Institution has been offered to Astronomer R. H. Tucker, of the Lick Observatory, at present in acting charge of the Salter, during the absence of the director. The plan of observing is the design of Lewis Boss, director of the Dudley Observatory at Albany, who has been engaged for many years in the observation and reduction of a large and accurate fundamental catalogue of stars. The work of the Southern Observatory will inchide the stars that are too far south to be measured at the observatories of the northern hemisphere. It is expected that three years will be required for the plan, and the Southern station will be located either in New Zealand, South America, or South Africa. The party wilt fltcattons of jirobably consist of seven observers, several of whom have already Ijeeii cngjiged. The selection of one of the Lick Observatory staff for the prosecution of this work is one of the instances of the recog- nition of the standing of this institution in professional work that have not been uncommon of late. The requirements of this particular plan are mainly those of experience, technical skill, and persistence in the execution of a scheme of work. The work of a large observatory is very much specialized, just as professional work has developed in other tines. It was as an observer, specially trained, that Mr. Tucker was invited, 6ftecn years ago, to join the Lick Observatory force, and to take charge of the Meridian Circle and Its work. Three quarto volumes have been since published, entirely devot- ed to the results of the observations made with this instrument during this period at the Lick Observatory. The work is of the character that has been fundamental in the development of our knowledge of the universe of stars and in tracing the motions of the planets of our complex solar system. The larger observatories in all parts of the world have always a force of astronomers working along this Hne, The smaller observatories rarely do any of this class of work. This present expedition suggests, in a way, the early trip of Lieutenant Gu.Liss to Chile, to observe the Southern stars; and the much more extensive and successful scheme of Dr. B. A. Gould, both of which eventually resulted in the founda- tion of national observatories at Santiago. Chile, and at Cor- doba, Argentine Republic, respectively. There were earlier expeditions to the Cape of Good Hope, the first of La Caille, and, later, one of Hkkscuel. which led to the establishment of the Royal Observatory at Capetown, now one of the finest in the world. The present scheme is expeditionary only, and the equipment will be brought back to this country when the spe- cific work is completed. The large Pistor and Martins Meridian Circle, of the Dud- ley Observatory, will be used for the Southern plan, and it introduces some feeling of sentiment, from the fact that the first professional observations of the astronomer, who is to take charge of this work, were made with that instnmient. Should San Luis, in the Argentine Republic, be finally selected as the observing station, there would be additional Astronomical Society of the Pacific. 49 fitness in the working out of the scheme, since it was from the National Observatory at Cordoba, two hundred miles dis- tant, that the observer came here, fresh from nine jears* serv- ice under the Southern skies. The Mills Expedition, of the Lick Observatory, is now located at Santiago, under the charge of Dr. H. D. Curtis; and while the Cordillera of the Andes would lie between the two stations, making a barrier of no ordinary magnitude, the two stations might easily get into touch with each other, by exchange of compliments. The work of the two stations does not conflict in any way ; the established one is for the physical investigation of Southern stars, by means of the spectroscope ; the new one will confine its work* to the measurement of the positions of the stars. — San Jose Mercury, January 24th, NEW PUBLICATIONS. Abetti, Antoxio. Osservarioni Astronomische fatte all' Eqiiatoriale di Arcetri nel 1906. Publicazioiii del R. In- stitnto di Stiidi Siiperiori Practici e di Perfeztonamenio in Firenze. R. Osservatorio di Arcetri. Fascicolo No. 23. Pirenze. 1907, 8vo. 90 pp. Paper. Annales de L'Observatoire Royal de Belgiqiie. Nouvelle Serie. Annales Astronomiqiies. Tome XI, Fascicule I. Bruxelles. 1907. 4to. 95 pp. Paper. Annales de L'Observatoire Royal de Belgique. Nouvelle Serie. Physique dii Globe. Tome III, Fascicule HI. Bruxelles. 1907. 410. 182 pp. Paper. Annales de L'Observatoire de Bordeaux. Tome XIII. Paris. 1907. 4to. A 30 + B 30 + 356 pp. Paper. Annuaire Astronomique pour 1908. Observatoire Royal de Belgique. Bruxelles. 1907, izmo. lii + 316 + 272a pp. Qoth. BoHLiN, Karl. Versuch einer Bestimmung der Parallaxe des Andromeda-Nebels. Astronomiska lakttagelser Och Uii- dersokningar A Stockholms Observatorium. Band 8. Nr. 4. 1907. 4to. 70 pp. Paper. De Sitter, W. On the Libration of the three inner large satellites of Jupiter. Publications of the Astronomical Laboratory at GroniiiKeii. No. 17. Groningen. 1907, 8vo, 119 pp. Paper. Eberhard, G. Untersuchiingen iiber den Spektrographen IV des .'\strophysikalischen Observatorium s. Publikalionen des Astrophysikalischen Observatoriums zu Potsdam. Band 18. Zweites Stuck. irK)7, 4to. no pp. Paper. Fagerholm, Erik. Uber den Stemhaufen Messier 67. In- augural Dissertation. Upsala. 1906, 8vo. S3 pp. Paper. FoHNi, Giovanni. Nuove Determinazioni della Latitudine del Reale Osservatorio Astronomico di Brera. No. XLIII. Publicazioni del Reale Osservatorio di Brera in Milano. Milano. 1907. 4to. 27 pp. Paper. Publications of the Astronomical Society, &c. 51 Heliographic Positions of Sun-spots Observed at Hamilton College from i860 to 1870, by Dr. C. H. F, Peters. Edited for publication by Etiwix B. Frost. Published by the Carnegie Institution of Washington. Washington. 1907. XIII + 188 pp. Paper. Les Observatoires Astronomiques et les Astronomes, par P. Stroobant, J. Delvos.\l, H. Phimppot, E. Delporte, et E. Merlin. Bruxelles. 1907. 8vo. 316 pp. Boards. Observatoire de Bordeaux. Catalogue Photograph ique du Ciel. Coordonnees Rectiligiies. Tome II. Paris, uioy. 4to. Premier Fascicule, 14 + 205 pp. Deuxietne Fascicule, XV + 22 pp. Paper. Observations faites an Cercle Meridien en 1905. Observatoire D'Abbadia. Observations, Tome V. Hendaye. 1907. 4to. v + 305 pp. Paper. Observatoire Jarry-Desloges. Ob.servations des Surfaces F'lanetaires. Fascicule I. 1907. Paris. 1908. 8vo. 121 pp. Paper. Petkhs, J. Neuer Fundamentalkatalog des Berliner .Astro- nomischen Jahrbuchs nach den Grundlagen von A. .'\uwEKS fiir die Epochen 1875 und 1900. \'er6ffentlich- imgen des KonJglichen Astrononiischen Rechen-Instituts zu Berlin. No. 33. Berlin. 1907. 4to. viii -(- 116 pp. Paper. Tltcker. R. H. Meridian Circle Observations made at the Lick Observatory, University of California. 1901-1906. Publications of the Lick Observatory. Volume X. Sac- ramento. 1907. 4to. 269 pp. Cloth. ViARo, B. Osservazioni .\stronomiche fatte al Piccolo Meri- diano Hi .'\rcetri nel 1905-1906. Pnblicazioni del R. Insti- tuto di Studi Snpcriori Practici e di Perfezionamento in Firenze. R. Osservatorio di Arcetri. Fascicolo No. 24. Firenze. 8vo. 61 pp. Paper. Minutes of the Special Meeting of the Board of Direc- tors OF THE Astronomical Society of the Pacific, ^m Held in Room 6oi Merchants Exchange ^M Building, San Francisco, on Satur- ^H DAY, November 30, 1907, Al the meeting of November 30, 1907, (the minutes with this excep- tion have been published in No. 1 17 of these Puhlicaliofts.) ihe Bruce Gold Medal for the year 1908 was awarded to Professor Edward C. Pickering, Director of Harvard College Observatory. The following certificate of bestowal was signed by all Directors present : — SEVENTH AWAHP OF THE BRUCE MEDAL. t of avRrdinK the medal for 1 >w«(iD C. PicKBUiio, fnr diiti' ItDSOK, 5. D. TUWBLI Tn answer to a letter addressed to Professor Pickeiing, notifying him of the action of the Directors, the following; letter of acceptance was received : — CAHBRiunt. Mass.. January 3, 1908. Mt Dea* Sik:— Your letter of January ill, annmineinf thai Ihe Bruce Medal for the year looS baa been awarded lo me. hai been received, Plea« convey lo the Board of Dirertori of the Astronomical Soeiely of the Pacilit my Bicat appreciation of the diitinguisbed honor thus conferred upon me. Il iffordi me great pleasnie to have my name thui associated with that of Miu Biucn and thoie of Ihe eminent utronoraeri to whom the medal haa already been awarded. Youri very alncerely. Edwaid C. PlCKUlHO. Dr. Rtri t Astrofiomical Soe< af tht Fact MiNUTF-S OF THE MEETING OF THE Bo.\RD OF DIRECTORS, HeLD AT THE Chabot Observatory, Oakland, Cal., ON January' 25, 1908, at 8 p,m. A quorum was pre.senl. President Cushing presided. The minutes of the meeting of November 30, 1907, were approved. The Secretary reported that he had notified Director E. C. PlCKEK- INC, of Harvard College Observatory, that the Directors of this Societjr had awarded him the Bruce Gold Medal for the year igo8, and that - PicKEHiNC had accepted the medal. Astronomical Society ofthe Pacific . 53 The following were elected lo membership : — Miss Alice Joy 2521 Piedmont Avemie, Berkeley, Cal. Miss Elizabeth E. Gabvey. ..2440 Hillside Avemie, Berkeley, Cal. Mr. W. F. Meyer Suidenls' Observatory, Berkeley, Cal. The President was aiithoriied to appoint an Auditing Committee of three members, and 3 Nominating Committee of five members. It was moved, seconded, and carried that the Library of Stanford University be given Volume XV of the Society's Publications to replace their original volume, which was lost in the fire of April, 1906. It was moved, seconded, and carried that the following he the schedule of prices for single copies of the PublUations: — One dollar for non-members. Seventy-five cents for dealers. Fifty cents for members. The Secretary was instructed to place $500 insurance upon the Society's property. A lelter from Professor W. Steadman Alois, offering some addi- tional books for our Library, was read. The Secretary was instructed to convey the thanks of the Society to Professor Alois, and to select from the hsl sent those hooks deemed useful to the Society. Adjourned. Minutes of the Meeting of the Society, Held in Chabot Observatorv, Oakland, Cal., on January 25, 1908, at 8:30 P.M. President Cushinc presided. Upon calling the Society to order he announced that the meeting would be devoted to informal discussion of current astronomical problems. The Secretary read Professor PiCKEaiso'a letter accepting the Bruce Gold Medal, which had been awarded to him for the year 1908, Professor Cbawfohb made a few remarks upon the "Supposed Dis- appearance of Saturn's Rings." Later in the evening Professor Aitkem made some remarks upon this same subject, and also gave a short talk upon his observations of the "knots" on Saturn's ring. Professors Pebrime and Ajtken, who had just arrived from the eclipse expedition to Flint Island, gave some very interesting accounts of their experiences. Professor Aitken read a short preliminary paper upon the eclipse, prepared by Director Campbell. The paper was dated from the Golden Gate. Adjourned. k OFFICSRS OF THE SOCIBTY. Mr, Ch*i. S. Cliibino Mr. A. II. Baicock Fvit Vict Mr, W. W. Cahfsul SttMd Via Mr. G«o E. HALt Tiiird VmPretiina Mr. fi, T. Cbawfom. (Sludenll' Observatory, Berkeley) SrrrtUrj Mf, B. G. AiiHK (Mount Homnton. Cil.) StcnUrj Mr. F. H. ZiEL TrtioMnt Beard tf Dirtciari — Meiirs. Aitkem. Babcock, Buhcuxjutu. Ciuraiu. CxKUt. C«AWfoitii, CusHiNb. Hale. Rich*»dson, Towblet, 2hl. FinnKCt Committte — MeaBrs. RrcH*BDso», Cidckh, Bu«ckb*i.tk». Cammiiice an FvbUtalioK—Maitt. Aiikih, Townley, Madoiill. ^^H Library CBmrniltii—tHenn. CuAwroiD, Iivihg, Townut. ^^H Ccmmitic, on the Comii-ilednl — titian. Caupbeix (ex-afficio). BuickM^^H „ ^M NOTica. The .ttemion of new membeti is called lo Arlicle VIII at the By-Lawi. which calendar ;»r. This rule is necessary m oriler to make nur bookkeeping u simple s* possible. Due) (enl by mail should be directed title-pan and contents of the preceding number, will also be sent lo the members, wbo can then member wiibin the United Slatea can lAiain books from the Socieiy'a library by sending bi« library card with ten cents in stamps to the Secretary A. S. P.. Students' Observatory, Berkeley, CaL, who irill return Ihe book and [he eard. The Committee on Publication desires to say thai the order in which papers ■re printed in the PubinatioKi is decided simply by convenience. In a aenenl way. those papers are printed first which ate earliest accepted far publicatioo. Papers intended to be primed in a given number of the PubficaliaHi shanld be ia the hands of the Commitlee not later than Ihe lolh of the monlli preceding date of publication. It is not possible to send proof sheets of papers to be printed to authors whaie residence i> nnt within the l/nlled States. The lespotuitnlit^ for ths views eipressed in Ihe papers printed, and foe the form of their expTEtsiBn, rcMf with the writers, and is not assumed by the Society itself. The titles of papers for reading ahould be communicated to either of the Sec- retaries as early a» paiMible. a! well as any changea in addresKS. The Secre- tary in Berkeley win send to any member of the Society suitable suiioneir. atamped with the seal of the Society, at cost price, as follows: a block of letter prices include postage, and should be remitted by money-order or in U. S. postage ■tampL The sending) are st the ri«k of the member. Those members who propose to attend Ihe meetings at Mount Hamilton during [he Bummer should communicate with "The Secreury Asvronomicil Socieir at the Pacific." Students- Observatory, Berkeley. Cal.. in order that arrangement* nlf PUBLICATIONS ISSUED BI-MONTHLY. ^^H iFtbrmiry, /Ipril. June. Atguil. Oclabtr. Dtctmbir.) ^^^ i •• ;./V YOJ- contributed to and assisted in editing its publications over the entire period of its existence. They have lectured for us and have in many ways otherwise contributed to the success of the Society. Above ail, they have extended to the members of the Society the privilege of meeting at the Lick Observatory and of seeing the practical workings of that great institution, a privilege the equal of which probably no other like society can enjoy. Our Society now possesses an endowment of nearly twenty thousand dollars. The income from a considerable portion of this is being devoted towards onr Publicalions. At the time of the great fire in San Francisco, of April 18, 1906, the Society had a very considerable library, which it maintained in its rooms in the building of the California Academy of Sciences. While in the destruction of this library the Society suffered severely, the generosity of various members and societies has done much to repair this loss. I take pleasure in announcing that the library of the Society now consists of about two hundred and eighty-five bound volumes and about seven hundred pamphlets. Among the many contributions to the rehabilitation of our library I desire to refer particularly to that of Professor W. Stearman Alois, F. R. A. S., of Oxford, England, who contributed fifty vol- umes, many of which are rare, and all of which are valuable; and to that of Professor Edward S. Holdex, who has sent a.Tfflltiable contribution of books and pamphlets. Nearly all of tJitJargC: observatories, including the obser\'atory at Green- wich; United States Naval Observatory at Washington, and the Lick 'Observatory, have sent either complete sets of their. oWn publications or sets as nearly complete as they could spare. Ih ■ specially mentioning the foregoing contributions I have not forgotten the many other generous gifts to our Society. By the courtesy of the President of the L'niversity of California these books are housed at the Students' Observatory at that institution. The rapid rebuilding of San Francisco brings to mind the desirability of obtaining for the Society permanent rooms in San Francisco, where the library can be maintained' and Tnadb accessible to those desiring to use it. [ 58 Publications of the Among the funds of our Society is one contributed by the late Catherine Wolfe Bruce, of New York, to be used for the purchase of a gold medal to be awarded, regardless of race or sex, for distinguished services to astronomy. By the terms of the trust creating this fund the medalist is chosen by the Board of Directors of the Society from persons nominated by six of the most prominent observatories of the world — viz.: Berlin, Harvard, Greenwich. Lick, Paris, and Yerkes. This medal has been awarded in the past successively to Professor Simon Newcomb, Professor Arthur Auwers. Sir David Gill, Professor Giovanni Vibginio Schiapahelli, Sir William Huggins, and Professor Hermann Carl Vogel. It now becomes my pleasure to announce the seventh award of this medal to Professor Edward C. Pickering, Director of the Harvard College Observatory. While the name of Professor Pickering and his connection with Harvard College is so well known to all who take any interest in astronomy, it will not be out of place to here refer briefly to his career and to some of his many achievements. Edward C. Pickering was bom in Boston, July 19, 1846. He graduated at Harvard College in 1865, and acted as a teacher of physics at the Massachusetts Institute of Technology for a period of ten years. Professor Pickering's advent into astronomy came in the year 1877, when he became Director of the Harvard College Observatory. Prior to that time he had been more of a physicist and mathematician than an astron- omer. At about the time Professor Pickering became Direct- or of Harvard Observatory, the rapid development of stellar photography and of stellar spectrum analysis emphasized the importance of the department of astrophysics. It is much to the credit of those who selected our medalist for the important position, which he has so long occupied, that they so early recognized the fact that the new director must be a chemist and a physicist. During the nineteenth century scientific development along almost every hne has been very rapid, and in no science is this more marked than in astronomy. The great development of photography and spectroscopy brought greater demands on the intelligence of the astronomer along lines which during the early part of the nineteenth century were hardly dreamed of. Professor Pickering did not hesitate to start in imme- dstronomtcal Society of the Pacific. 59 diately after his advent into his new position to undertake works of vast magnitude, and in carrying his plans into effect he has shown the most unbounded energy, as well as unusual executive ability. In his first annual report he announced his intention of undertaking the extensive work of reducing Argelander's com- parative observations of variable stars, by measuring the brightness of the comparison stars, and thus determining the true brightness of the variables as given in the "Bonn Obser- vations." This work he published some years later. The first paper on the subject was published in 1880, wherein, from mathematical reasoning, he proves that the variability of stars of the Algol type is due to a non-luminous body revolving around the star; the results he obtained from the ratio of the diameters of Algol and its satellite are very closely accordant with those announced by Vogel some years later. Professor Pickering's name will always be associated with the work carried on under the name of the Henry Draper Memorial. Professor Hf.nry Draper was a distinguished scientist, who was especially noted for his labors in celestial photography. In the year 1886 his widow made a liberal provision for carrying on researches in stellar spectroscopy as a memorial to her late husband. It is natural that the work proposed by her was along Sines of investigation in fields which her husband had hoped to explore. The trust was placed in the hands of Professor Pickering, who was thus enabled to work with sufficient means to carry the task into execution. The investigations were planned to cover the entire sky, and involved an investigation into the conditions and physical properties of the stars as revealed by their spectra ; and as the scheme was developed four telescopes were established for the observations, two at Cambridge and two at Arequipa, Peni. This work has been prosecuted to the present time with amazing industry. Under the direction of Professor Pickering, since its estab- lishment, the Henry Draper Memorial has developed several new and unique lines of work. The objective prism and doublet have been substituted for the slit spectroscope and single lens, and by this means the spectra of a large number of stars are photographed simultaneously instead of singly by the former method. These photographs have been repeated until every portion of the sky has been covered. By this method a photo- graph of the spectrum of every star in the sky permanently brighter than the ninth or tenth magnitude, besides many thousand that are fainter, has been obtained. These plates have been carefully examined, and as a result a large number of objects having peculiar sijectra have been discovered. To illustrate one of the results of this work it may be inter- esting to state that of eight novx which are known Co have appeared during the sixteen years prior to 1902 two were vis- ible to the naked eye. All the others were found from the Draper photographs, and but for these photographs would probably never have been discovered. The minor planet Eros was discovered in 1898 by Witt, but ■ the examination of the Harvard photographs enabled Professor PiCKtKiNG to announce that it could be detected on fifteen or sixteen plates taken from 1S93 to 1806. and that the spec- trum photographed in January, 1894, was, like that of other planets, and the Sun, of the second type. A photograph taken in 1894 shows the planet as a long trail, while the images of the stars are round. The vast work carried on at the two observatories under the name of the Draper Memorial included repeatedly photograph- ing all portions of the sky, both Northern and Southern. By this means a map of the sky, showing all the brighter stars night after night, was made. The records of these observa- tions furnish a complete history of the heavens every year since 1890. It is obvious from this that when any new object is discovered its history can be traced through these photo- graphs. No such collection of photographs has ever been made, and the collection is as unique as it is vast. The number of these photographs exceeds fifty thousand, and when we consider that these figures represent repeated surveys of the entire heavens — spectrographic, photometric, and photographic — and that these extend over a large number of years, one cannot but be impressed by the vast amount of work done in this undertaking, and with the energy and abilitj- with which it was carried into effect. In the year 1S89, Miss Catherine Bruce, of New York, placed at the disposal of 1-tarvard University a large sum of money to purchase a 24-inch photographic telescope. When this telescope was completed it was mounted at the Arequipa attronomtcat aocteiy of Observatory, where it has since been regularly used. This was a most welcome and material acquisition to the observa- tory, and an immense number of photographs have been taken with it. The generous donor of this telescope was the same lady whose high appreciation of astronomical, efforts caused her to present to the Astronomical Society of the Pacific tlie fund known as the Bruce Medal Fund, to which I have already referred. The medal now presented to Professor Pickering is awarded from that fund in accordance with the directions from Miss Bruce. It is interesting to know that the generosity of Miss Bruce in presenting the telescope above referred to undoubtedly assisted our medalist in his untiring efforts, and its use must be regarded as a factor in enabling him to win the medal now presented to him. Thus, Miss Bruce has assisted astronomical science in two different directions, and on both sides of our continent. Greatness In a commanding general consists not alone in individual effort and accomplishment, but in the ability to utilize the efforts of others. Professor Pickerino's accom- plishments are along both of these lines. During his director- ship of Harvard Observatory it has risen from a comparatively small institution to its present position as one of the leading observatories of the world. He has organized its work and directed it in fields of great usefulness, and in such a manner as not to conflict with, or overlap upon, the work of other observatories. Through his foresight, a finely equipped observatory has been established in Peru under most advantageous climatic conditions, thus making Harvard Observatory, in this respect, the best equipped of all observatories. In dwelling particularly on the genius of our medalist for organization, and for utilizing the efforts of others, the writer does not desire to detract in any manner from his many purely personal triumphs as an astronomer. His thorough grasp of the many sides of astronomical work cannot be better illus- trated than by referring to his ability to create important instruments for astronomical work. Among these is his meridian photometer, an instrument for measuring and com- paring the brightness of stars. While this instrument must Publications of ike be regarded, to some extent, as an adaptation of previously cjtisting instruments, Professor Pickering has introduced so many important modifications as to make it in reality an original instrument. Our Society has every reason to feel greatly proud of the manner in which .this medal has been previously awarded. The list of awards is a roll of honor on which any scientist would be pleased to find his name inscribed, yet the writer knows that there is a feeling among members of our Societj' that the award to Professor Pickering has been too long delayed. In closing it may not be out of place to state a few of the many reasons why this medal is awarded to Professor Pickering. As Director of Harvard College Observatory, he has given evidence of rare executive ability, of a remarkably clear and comprehensive insight into the great problems of sidereal astronomy, and of great resourcefulness in devising the most promising methods of attacking them, and in designing new instruments to carry out these attacks. This unusual combination of gifts has enabled him to organ- ize effective work on a large scale in at least three distinct though related fields — stellar photometry, stellar photography, and the study of stellar spectra. Thus, the Harvard College Observatory stands unique among the astronomical institutions of the world in possessing a vast library, to use Professor Pickering's own happy comparison, of photographs of incom- parable value, containing a complete history of the aspect of the entire heavens for nearly twenty years, and a complete record of the spectra of at least all stars as bright as the eighth magnitude. In its record for the discovery of new and variable stars the observatory also stands without a rival, and only the Potsdam Observatory approaches it in the field of determining the photo- metric magnitudes of the Stars. To develop such an institution, and to successfully direct the execution of such extensive and important researches would seem to give sufficient exercise for the energies of the ablest man; but Professor Pickering is also an enthusiastic and, tireless observer, and his personal researches, especially in the study of variable stars and in the photometric measures of stars, particularly with his ingeniously devised meridian Astronomical Society of the Pacific. 63 photometer, constitute contributions to the advancement of astronomy of which any investigator might well be proud, and which in themselves would afford ample ground for the award of this medal. The foregoing brief narrative will, I trust, to some extent show the wisdom of our Board of Directors in awarding this medal to Professor Pickering. Our medalist is still relatively a young man, and while his achievements have been vast, they are by no means ended, and we have every reason to believe that what has been done is but earnest of what will be done by him. In the absence of Professor Pickering, I request you, Mr. Secretary, to transmit this meda! to the distinguished scientist to whom it is awarded, with the congratulations and best wishes of the members of this Society, that he may long live to enjoy bis honors so fairly won. THE CROCKER ECLIPSE EXPEDITION OF 1908 FROM THE LICK OBSERVATORY, UNIVER- SITY OF CALIFORNIA. By W. W. Campbell, The Moon's shadow for the total solar eclipse of January 3, 1908. fell upon the F.arth at sunrise in longitude 155" east and latitude 1 1 ° north, swept easteriy across the central Pacific Ocean, and left the Earth at sunset on the western coast-line of Costa Rica, The shadow path crossed only two known landmarks — Hull Island, about seven hundred miles north of Samoa, and Flint Island (British), in latitude 11° south, four hundred and fifty miles northwest of the Island of Tahiti. The eclipse lasted sixty per cent longer and the Sun was much nearer the zenith at Flint Island than at Hull Island ; and both were equally difficult of access. On account of our position, on the Caiifornian coast of the Pacific, and in view of our considerable experience in eclipse observation, there existed amongst astronomers a feeling that the Lick Observatory should, if possible, take care of this Hicattons of the eclijist. This feeling was intensified by tlie knowledge that no other observatory was planning to send out an eclipse expedition. Our duty in the matter was in harmony with the strong desire to maintain, as far as practicable, the continuity of our eclipse series of observations, and to undertake the solution of certain definite eclipse problems. The subject was brought to the attention of Mr, Williau H. Ckocker early in the year IQ07, and he generously under- took to defray the expenses of an expedition to Flint Island — the ninth Crocker Eclipse Expedition — provided a practicable method of transport could be found. There is excellent steamer service between San Francisco and Tahiti ; but Flint Island is not on any steamer route. Regular steamers in the South Seas could not be induced, even for a consideration, to go a few hundred miles out of their way. because of insurance compli- cations and of government mail contracts on fixed schedules and over definite routes. The chartering nf a steamer exclu- sively for this purpose was prohibited by the cost. At this juncture it seemed to me that an appeal might with propriety be made to the Navy Department of our Government to transport the expedition. President Wheeler was pleased to approve this plan and to present my appeal. In response, the department expressed its desire and readiness to meet our requirements fully. It was arranged that the U. S. gunboat "Annapolis." under command of His Excellency, Captain C. B. T. Moore, U. S. N., Governor of Tutuila, Samoan Islands, should meet us at Tahiti, transport the expedition to Flint Island about four weeks before the eclipse, and, two days after the eclipse, re-embark and carry the expedition back to Tahiti. It was my first pleasure and duty, on returning from Flint Island, to express to the department not only our thanks for this invaluable service, but our admiration for the clear-cut and business-like manner in which Governor Moore and his staff carried out the letter and the spirit of the department's instructions. It seemed very desirable that the observing programme should include a study of the heat radiations of the corona, by means of a bolometer. This important line of investigation had been inaugurated at the eclipse of iQOO by Mr. C. G. Abbot, of the Smithsonian Institution Observatory. This Astronomical Society of the Pacific. 65 fact, and liis extensive experience and recognized skill in the use of the holometer. made him the logical and best observer for this eclipse work. Accordingly, in April, 1907, it gave me pleasure to urge upon Dr. Walcott, Secretary of the Smithsonian Institution, and Director Abbot, of the Astro- physical Observatory of the Institution, the desirability of dispatching an expedition to secure these observations, and to invite the suggested expedition to share in the travel and subsistence arrangements already under way for the Lick Observatory expedition. The proposal met with their approval. The scientific plans of the two expeditions were to be essen- tially independent, the travel and subsistence expenses to be shared on the basis of the number of persons in the two parties. Professor E. P. Lewis, of the Department of Physics, Uni- versity of California, was invited to join the Crocker Expedi- tion by virtue of his great skill in spectroscopic researches, in order that he might photograph the spectrum of the corona with his large quartz spectrograph. The two expeditions sailed from San Francisco on November 22d, on the steamship "Mariposa," of the Oceanic Steamship Company. We numbered eight persons, and there were thirty-five tons of scientific instniments, tents, food, lumber, and general suppHes. The party consisted of Director and Mrs. Campbell, Astronomers Pekrine and Aitken, and Assistant Albrecht, of Mt. Hamilton: Professor Lewis, of Berkeley ; Director Abbot, of Washington, and his assistant. Mr. A. F. MooHE, of the University of California. The twelve-day passage to Tahiti, in latitude 17°. 5 south, was comfo^able, but without special incident, as no ships were sighted after the second day out, and no land until the eleventh day, when three very interesting islands of the Paumotu group, or Dangerous Archipelago, were passed. We reached Papeete, Island of Tahiti, on December 4th. The "Annapolis" came into the harbor on the morning of December 5th. By invitation extended through Governor MooRE, our party was joined on board the ".Annapolis" by Professor Benjamin Boss, in charge of the U. S. Naval Observatory at Pago Pago, formerly assistant in the observa- tories at Washington and Albany. Three busy days in Papeete were devoted to transferring our freight to the warship, secur- ing a supply of mineral drinking-water, fruit and other perish- ables, a siirf-boat for landing, and picking up our Tahitian carpenter, cooks, and laborers. We sailed for Flint Island on the evening of December 7th. We approached Flint Island at noon on December 9th. with very considerable anxiety. On the "Mariposa" and in Papeete we heard much of the difficult and dangerous surf landing. The captain of the Tahiti schooner which runs to Flint Island about twice a year explained that landing was possible at only one point, on the northwest side, where a narrow and shallow passage into the flat coral reef had been blasted out ; and if the surf were running high at that point we must wait on- board-ship until it subsided. This was true even when the surf-boats carried nothing more valuable than gunny-sacks full of cocoanuts and copra. The situation could be more serious for scientific instruments. The visible parts of Flint Island are entirely of coral con- struction. The waves break on the outer edge of a flat and level reef, whose average width is perhaps two hundred feet, whose height appears to be closely that of quiet water at high tide, and which nearly or entirely surrounds the island. At the outer edge the dip of the reef into deep water is remarkably steep. Sloping up from the inner edge of the flat reef is the dazzling white beach of broken coral, perhaps one hundred feet wide, which encircles the island, except that on the east side there are many irregularities in the way of rough and tilted reefs of solid rock not covered by broken coral. The entire area inside of the white beach consists of broken coral, more or less disintegrated, and is densely covered withlrees, The form of the island is roughly that of a lozenge or kite, with greatest width east and west, nearly one mile, and length north and south slightly over two miles. Its greatest height, above mean sea-level, is twenty-two feet at the point, near the land- ing, where the buildings of the leasing company are situated. The average height is said to be thirteen feet. A few years ago the northern four fifths of the island were cleared of native trees and planted to cocoanut trees. There are no settled inhabitants. The lessees, Lever's Pacific Plan- tations Limited, maintain there an English manager and Li Astronomical Society of the Pacific. 67 P about twenty-five native men and women, all engaged exclu- sively in the manufacture of copra. The capable manager, Mr. E. F, H.awk, rowed out to the "Annapolis" with the pleasing intelligence that in his twenty- seven months' residence on the island he had never seen the surf running lower. Accordingly, with the help of the native boatmen and laborers, and of many of the ship's men, the land- ing in the surf-boats was rushed. By eight o'clock our forty tons of effects were on the beach and the "Annapolis" had turned back to Tahiti. The contents of our more than three hundred numbered packages were known in detail. This fact, and the placing of the large veranda and several rooms of the manager's bungalow at our disposal, made the starting of life on the island easy. It would be a dull imagination indeed which, at our first dinner, should not travel rapidly, to the accompaniment of roaring surf, the great cocoanut grove filled with nuts and noisy birds,' native figures moving noiselessly about, and the knowledge that a month of strenuous and inter- esting labor had begun. The site for the station was selected at a point about two hundred feet directly east of the manager's bungalow, in the midst of the cocoanuls ; a few missing trees here and there affording just sufficient unobstructed sky for convenient adjust- ment of the eight groups of instruments. The soil, of old coral, was, nearly everywhere in our camp, covered with rich grass. A tramway running from the landing slip immediately past the camp-site greatly facilitated the bringing up of our heavy supplies. The iron-roofed buildings, and the planta- tions' and our own steel tanks, affording, to our relief, an abundant supply of pure drinking-water, were less than one hundred yards away. The surrounding forest made an effi- cient break against winds from all directions ; but, fortunately, the wind that rustled the treetops extended its cooling effects to the observers at their work. We were eight hundred and thirty feet (the meridian of the transit instrument) from the outer edge of the reef, and the altitude of the site was sixteen feet above mean sea-level. The ridge, altitude twenty-two feet. Publications of the bearing the bungalow and the copra houses, was between ns and the beach. The terrible hurricane of 1906 had brought the seas up to the crest of the ridge, throwing some of ihe buildings off their foundations, but the waves did not reath our position. This was comforting, inasmuch as the great loss of life and property caused in the South Seas by the hurricane is still the prevaihng topic of conversation in that region. The sky when clear was remarkably pure and blue, resembling the Mt. Hamilton sky at its best. AH in all, the conditions at the station, local and general, were better than we could have expected, though we were always conscious of the fact that the chances for clear sky at the critical time were not greater than two out of three. As a result of prior correspondence with, and at the sug^s- tion of, the American Consul at Tahiti, it was planned to pro- vide cocoanut-thatch huts for the living-rooms, dining-room, kitchen, etc. Lumber for their frames, taken from San Fran- cisco, was quickly put in place by our carpenter and helpers; and the natives brought cocoanut fronds, wove them into thatch, and fastened them on the roof- and side-frames. The eight houses were completed, furnished with the necessan' shelves and tables, and occupied as rapidly as each was com- pletedv — all in four days. They were so easy of construction, so comfortable in tropical sun and rain, in fact so thoroughly adapted to their purposes, that tlie publication of a few addi- tional details may be of value to future expeditions in tropical locations where thatch is available. Each of the six sleeping-huts was 10 x 14 feet, witii side- walls 7J4 feet high. The gable roof was slightly steeper than an ordinary shingle roof. The thatch on the roof should be spread thickly, to turn the rain, but the walls need only a one- thickness covering. We found it advantageous to leave open the two side walls between the limits 6 feet and 7'-^ feet above the ground, as this afforded better air circulation. A strip of cloth suspended by and sliding on a wire served as a door. Good dimensions for timbers are : Six side-posts, 3x3 inches, let into the ground a short distance; two gable-posts and one door-post, 2x3 inches, also let into the ground; two side- beams, 3x3 inches (with allowance for one-foot gable-roof projections) ; three cross-beams, 2x3 inches; six rafters or %\ Astronomical Society of the Pacific. I each side, 2x3 inches (with allowance for one-foot eaves J ; one ridge board, i x6 inches; two boards on the lower ends of rafters, 1x4 inches. Total, 160 feet, board measure. Diagonal ties in the wall and roof sections, of soft steel wire, '/,g inch, can be put in place, with six-penny nails, in a few minutes. The natives are accustomed to fastening the thatch in place with strong wrapping twine, but we found six-penny nails more satisfactory in every way. Each hut accommodated the large cots, baggage, and conveniences for two men. The dining-room, 12. '£28 feet, had a thatch roof and gables, and mosqni to-netting ceiling, walls, and doors. Double-door entrances, such as are ■ used in connection with dark-rooms. would have been an improvement in keeping flies out. On a similar occasion we should construct two work-rooms, in the same manner, with thatch roofs and open sides, and also a food-supply hut. While the huts were in process of building, the pier for the Rcpsold altazimuth was constructed and the instrument mounted thereon ready for use; the first time observation hav- ing been secured on the evening of December nth. The grounds were cleared, the instruments and supplies were un- packed in the canva."! tents, and the foundations were made ready. The weather was fine, barring short rains, during the first twelve days on the island, and the work of assembling, erecting, and placing the instalments in approximate position and adjustment was well along toward completion. In fact, there remained essentially only the final and delicate adjust- ments, the repeated trials of the instruments, the training of the observers, and the thousand and one changes in details Which go to make np the difference between reasonably good results and those that are really worth while. The Smithsonian Expedition's observing station was selected by Director Abbot at a point on the beach about 1,200 feet northwest of ours, in order that his bolometric observations prior to the eclipse might have one half the sky unobstnicted ■ by trees. The progress of Mr. Abbot's preparations w^s analogous to our own. A few weeks before leaving California we learned with great pleasure that Mr, Francis K. McCi.ean. F. R. A. S., of Tunbridge Wells. England, son of the late F. K. McClean, TO Publications of the F. R. S., distinguished contributor, both scientifically and financially, to astronomical progress, would conduct an expedi- tion to Flint Island at his own expense. We looked forward to his coming with eagerness. His chartered ship arrived on December 23d. The party consisted of Mr, McClean, chief; Messrs. Brooks, Raymond, and Short, of Sydney ; and Messrs. Walker and Winkelmann, of Auckland, Their camp adjoined ours on the southeast. We found them to be 'helpful and congenial neighbors, and we were sorry to lose their companionship on January 3d. immediately following the eclipse. Their photographs were to be developed on ship-board. We have not learned as to the degree of their success, but wc trust that Mr. McClean is well satisfied with the results of their worthy and hard work. Mr. McClean most kindly brought Mr. Merfield, of the Sydney Observatory, to assist our expedition. The days following December 20th were for the most part cloudy, but the nights after December 25th were nearly all clear. The preparations, proceeding at a normal rate, were > completed in good time on the morning of January 3d. The "Annapolis" returned on the early morning of January ist, bringing Consul and Mrs. Dreher from Tahiti to assist in the observations, and an abundant supply of ice for the photographic work. A room in the bungalow was fitted up as a dark-room. This had been placed at our disposal by Manager H. Mortimer, who had succeeded Manager Hawk on December 19th. Mr. Mortimer was invited to assist In the observations. The forenoon of January 3d was alternately clear and cloudy, with the clearness much In excess. About ten min- utes before the eclipse was total, clouds formed rapidly, until the sky was densely covered. Just as the time-keeper called from his chronometer, "Five minutes before totality." a drenching rain fell, and all seemed lost save honor. At the end of two or three minutes the rainfall began to decrease and the clouds in the east gave signs of breaking. The signal "two minutes before totality" was called, as prearranged. Less than a minute before totality the slender crescent of the Sun showed faintly through the clouds, though a moderate rain was still falling. The rain and clouds grew rapidly lighter. riiE Nh V YO.- ■•■ ! init'LIC LIDRA till;'" . ■ "•(.' and the last drops fell at two or three seconds after totality began. Immediately after the beginning of totality the corona was faintly visible through the thin clouds. These continued to disperse rapidly. During the second quarter of the total phase the clouds were extremely thin, though a thicker cloud ohsaired the Sun near the end of the second quarter; and during the third and fourth quarters the sky was clear of clouds, but a thin haze could be distinguished. There was no wind. .■\bout ten seconds before totality, the rain having nearly ceased, Ihe order was given to the workman seated on lop of the outer of the two towers supporting the forty-foot camera to remove the tarpaulin from over the Sens. The order was executed promptly and the remnant of the Sun's crescent was fir.it seen by the observer inside of the camera just one second before totality, and he immediately called out "One second before."' The signal "Go!" was called by the observer at the instant when the crescent disappeared. Such of the instru- ments as were still covered, awaiting the end of the rain, — for example, the larger ccelostat, — were uncovered within a few seconds, and thu programme of observations was thenceforth carried through without a single slip. The twenty instruments, driven by seven clocks, and the eleven observers and two helpers did their work to perfection. Two spectro graphic exposures planned for the twelve seconds immediately pre- ceding totality were necessarily omitted, and some of the sensitive plates were thought to be damaged by getting wet in the sudden downpour. The remaining exposures were expected to give good results; and such proved to be the case when the plates were developed, during the following two nights. All of the instruments were in perfect focus and adjustment. This eclipse was a very "light" one, — not nearly so dark as those of 1898, 1900, and 1905, as observed by the writer. The accompanying views of the station are from photographs secured shortly after the eclipse was ovpr. The negative of the group of observers was unfortunately much underexposed. The > It had been arranged that IbU oblervEr should calt out "Ponr^lght <«onda before" and "Ninflfen jeoondi before riotalily]" whfn Ihe uneclipied creicent had certain definitt cnmi>uicd lenpba; but the unposiibility of uneoverini ihc ttoi I canvas covering of the outer tower supporting the forty-foot camera was removed before photographing that instrument. The repacking of the instniments proceeded rapidly, and, the surf being very favorable, the most valuable articles, such as chronometers, lenses, mirrors, prisms, and clocks, were put on- board-ship on the morning of January 4th. As soon as the last of the eclipse negatives was dry all were packed with extreme care and sealed in tin. These packages, accompanied by the observers in two surf-boats, were the last to go on board, at 11 o'clock of January 5th. By this time the surf had risen, one of the boats shipped considerable water, and the experiences of both boats in passing out through the surf were certainly exciting. The "Annapolis" headed at once for Tahiti, which we reached at daylight of the 7th. Our departure from Flint Island was not unmixed with regret. A few members of the party were heard to wish that they could remain longer to enjoy the wonderful beautj' of our surroundings, a result that strenuous eclipse duties did not adequately permit. Our camp-life was wholly devoid of un- pleasantness. There had been time on a few evenings for experiences that wi!l never be forgotten. A successful turtle hunt on the coral beach, in alternating moonlight and tropical downpour; a Christmas-tree, with presents and toasts supplied by friends who remained behind in Papeete ; a Christmas din- ner in which Mr. McClean's party and ours joined forces; and a poetic contest entered into by nearly all members of both parties, to determine who should be called the Poet Laureate of Flint Island. Every member of the party was well every minute, notwithstanding exposure to tropical sun and frequent drenchings; and this happy result is perhaps sufficient comment on the judgment and efficiency of the commissary department Six days on the Island of Tahiti were devoted to closing up the local business affairs, to observing for longitude at Point Venus, to sight-seeing, and to several exceptionally agreeable social matters. We sailed north on the 13th, and after a stormy passage entered the Golden Gate on the 25th. The instru- ments and eclipse photographs reached Mt. Hamilton uninjured early in February. Following is a brief description of the instruments, observ- ing programme, and results secured. The results obtained wifji \ each insi Astronomical Society of the Pacific. 73 will be published later each instrument and for each probli in detail. TIME, LATITUDE AND LONGITUDE, It was the intention that Dr. Aitken should observe Moon cubninations both before and after the full Moon of December 19th, with the Repsold altazimuth instrument, to determine the longitude of the station; taking into account the fact that the Moon's right ascension, as measured at Mt. Hamilton on four nights in October and November by Professor Tockeb, was o'.4i greater than the ephemeris value. Unfortunately, there were thick clouds at the times of transit on some ten successive nights, and only one culmination was observed, — on the night of December 25th. The resulting value of the longi- tude, 10" 7" irf.o west, is necessarily of small weight. Our two chronometers, transported from the clock of the Students' Observatory, Berkeley, to Flint Island, and back to the clock in Berkeley, gave a longitude of 10" 7° 11" west. A com- parison of time observations by transits secured on January 3d, at the eclipse station, with sextant observations of the Sun obtained at Point Venus, Tahiti, on January 8th. made the longitude of our station 10" 7° 16*. 8; assuming the position of Point Venus to be as quoted in t!ie "Connaissance des Temps." Dr. Aitken's observed meridian altitudes of a considerable number of stars on two evenings gave results for the latitude as follows: — December 13th, — 11" 25' 26".6 ± o".62 December 26th, — 11 25 27 .1 ± o .41 The adopted co-ordinates of the instrument, located near the center of the groups of instruments, are : — Longitude 10*' 07" 13* W, ± 4' Latitude — ii°25' 26".8 ±©",4 The concrete pier was left standing. The entrance to the landing-slip in the reef is estimated to be 1,200 feet northwest of the pier. Throughout totality the second-beats of the chronometer were called off by Dr. Aitken, as guides to the observers in the Lick and British parties. 3ngi- 74' Publications of the TIMES OF BECrNNING AND ENDING. The prejicted times of beginning and ending of total based upon American Ephenieris data, and the adopted longi- tude and latitude of the station were: — Beginning, 9" 22" 43' Greenwich mean time Ending, 9 26 44 " " •• The times observed by Dr. .^itken without telescopic assi!^ ance, and by Dr. Ai.nRECUT inside of the forty-foot camera agreed within a second, and were:— Beginning 9" 22" Ending 9 2(1 The observed duration, 3™ 52*. was 9' shorter than the ( dieted duration; and mid-totalit>- came 27* ahead of the predicted time. The observed excess of l!ie Moon's right ascension, referred to above, would account for fully 2 Publications of the bright lines. A Sciihoeder's metal mirror, belonging to the Lick Observatory, mounted on a clock-driven (at one half the diurnal rate) polar axis, reflected the light horizontally into the quartz image-lens. The collimator- and camera-lenses of quartz are of g.2''" aperture and one meter focus. The effective rectangular apertures of the two Cobnu quartz prisms an; 6 X 6.8™. The length of the spectrog;ram from Z? to A 3000 is 14'"", The slit was adjusted to tangency to the Moon's limb at a point 16° 42' north of the highest point of the image on the slit, as this was the mean of the positions of tangents to the two points of contact of the Sun and Moon. It was intended to obtain a spectrum of the first flash, but the rain prevented. The exposure on the coronal spectrum extended from o" 15' to 3"" 30*. The photograph shows a strong continuous spec- trum extending from k 3200 to A 5100. Here and there in the middle ultra-violet, and nowhere else, are very faint indications of superimposed dark-line spectrum, of the same width as the continuous spectrum. This width is 3.1"°'. Superimposed on the continuous spectrum are about twenty-five sharp lines, none of which appears to proceed from the chromosphere. Some are so faint that their existence may be doubtful, while others may be maxima due to the superimposed dark-line spectrum. Two rather strong bright-lines appear to be new. Dr. Lewis further finds from the photograph that the Sun is relatively much richer in ultra-violet light than the corona, from which fact the much lower effective temperature of the latter is safely inferred. The west Hmb of the Moon was made tangent to the slit just at the end of totality, and an exposure on the flash spec- trum,— overexposed on account of the duration being shorter than expected, — recorded the tips of some eighty strong, bright crescents projecting beyond the solar spectrum. A fuller description and discussion of Dr. Lewis's important results will appear later. THK I'OLARIGRAPHS. The effects of polarization in the coronal light were observed by Dr. Pehrine by means of four special cameras mounted I Astronomical Society of the Factfic. 03 on a clock-driven axis. There was the camera of 20^-2 inches focus, having a double-image prism in front of its objective, that was used at the eclipses of 1901 and 1905- The other three cameras, of 50 inches focus, were designed by Dr. PerRink and used, in 1905. in Spain. Two of these have plane- glass reflectors in front of the objectives to serve as analyzers, while the purpose of the third, pointed directly to the Sun, is to secure an unpolarized image of the corona as a standard of comparison. The aperture of this direct camera was reduced, so that the image obtained with it would be approxi- mately of the same intensity as the (unpolarized) images formed in the other two cameras after reflection from the plane-glass surfaces. The plane-glass analyzers were set at the angle of maximum polarization. Their principal axes were adjusted, one parallel lo a north -and -south line and the other to an ea.st-and-west line, through the corona. The performance of all the polarigraphs was exactly as planned. Mrs. Campbell and Mrs. Drehkr assisted in mak- ing the observations. The four scries of negatives, with exposures of from 2" to 60", apjiear to be perfect in every respect. They show strong polarization effects in the corona, perhaps even to the very edge of the Moon's image. All of our previous polarization observations were secured through clouds; but, so far as we may judge from a comparison with the present series, the cloud.s were without appreciable effect on the character of the images. It is hoped to make accurate photometric measurements of the polarization series of photographs. Mounted on the same axis as the polarigraphs was a photometer, in all respects resembling an ordinary camera with the lens removed. The light from the corona and surounding sky passed directly through the aperture to the photographic plate. Two plates were exposed when the sky was entirely clear of clouds. Small standard squares on the plates had been exposed to the light of the Hefner lamp on the preceding night. Using these standards as a basis of comparison, it should be possible to obtain a satisfactory measurement of the total effective photographic action of the coronal radiations. These plates contain the data for measuring the sky brightness surrounding the corona. Dr. Pebrine's examination of the negatives shows that the effective photographic radiations of the corona came almost wholly from its extreme inner parts,— from within i' or 2' of the Sun's surface. The requirements of a large eclipse expedition are many; but, as I have stated on a previous occasion, the astronomer who is charged with the duty of conducting its affairs is an optimist, for at al] points where he needs assistance there are men ready to help him. The present expedition is under many obligations. The first reference must be to the great service rendered by the Navy Department of our Government, acting through His Excellency, Captain C. B. T. Moore, U. S. N., governor of Tutuila, Samoa, who was in command of the U. S. gunboat "Annapolis." To meet us at Tahiti, to transport the expedition to Flint Island early in December, to come a second time to the island, re-embark and carry the expedition back to Tahiti, required an absence of seven weeks from his Samoan post of duty, — an interval but two weeks shorter than our absence from California. Special thanks are due to Governor Moore not only for the able manner in which the department's instruc- tions were carried out, but for the constant personal and pro- fessional attention that he gave to the needs of the expedition and the comfort of its members. Our cordial thanks are extended also to the able corps of officers of the "Annapolis" — Lieut. W. G. Bricgs, U. S. N. ^— . Lieut. H. B. Soule, U. S. N. ^HJ Dr. M. E. Lando, U. S. N. ^H Paymaster J. M. Hilton, U. S. N. ^^^ Warrant Machinist J. F. Green, U. S. N. The petty officers and the gallant crew rendered splendid and heavy service in transferring our freight twice in Papeete Harbor and twice at Flint Island. Lever's Pacific Plantations Limited, lessees of Flint Island, gave permission to establish the observing station on the island, and instnicted their agents in Papeete, S. R. Maxwell & Co. (Mr. BuNCKLF.y, superintendent), and their succes- sive managers on the island, Messrs. Hawk and Mortimee, to meet the requirements of the expedition in every possible manner. Their instructions were carried out most liberally. The native labor was available, at my call, for the landing and re-embarking of the expedition, for the erection of huts, and for many otlier duties. As previously mentioned, the resources of the bungalow were shared by us for several days, and one room in it was devoted to dark-room purposes. The supply of fresh water was divided with us, half a dozen great turtles were sent in to the commissary department, and a score of other valuable services were rendered by Mes.srs. Hawk and Morti- mer. Mr. Mortimer assisted in the observations. We earnestly thank the Lever's Pacific Plantations Limited and their officials, Mr. Bunckley, Mr. Hawk, and Mr. Mortimer, for the invaluable services that are here but imperfectly mentioned. The Government of Tahiti, acting under instructions from Paris, kindly expedited the transfer of our freight and baggage through the port of Papeete. Our country is worthily represented by the American Consul in Tahiti, Dr. Jui.ius D. Dkeher During the period of organ- ization he supplied me with reliable information and valuable suggestions on a varietj' of subjects relating to the work and living arrangements of the expedition. Prior to our arrival he had arranged a score of business matters, in accordance with my statement of needs, which enabled us to proceed promptly to Flint Island. Dr. and Mrs. Drehek were the guests of the expedition during eclipse week, and they assisted in the observations. The pleasures of our nine days at Tahiti were constantly added to by their thoughtful acts of kindness. Many favors were extended to the expedition by the Oceanic Steamship Company, acting through Captain H. M. Hayward, of the steamship "Mariposa." and his officers, through General Passenger Agent Cockroft, of San Francisco, and through Agent Meuel, of Papeete, Mr. J. Lamb Dotv, Mr. F. W. Wakefield, and Mr. and Mrs. F. W. Searby. all former residents of Papeete, supplied useful information and advice. Professor Benjamin Boss, in charge of the U. S. Naval Observatory at Pago Pago, Tutuila, was an efficient member of the expedition throughout our stay of twenty-seven days on Flint Island. C. J. Merfield, Esq., of the Sydney Observatory, was a capable and busy member of our expedition during the eleven days that the British party was on the island. Thanks are extended to Mr. McClean for his generosity in transporting Mr. Merfield from Auckland to the island and return, and for the spirit of comradeship and good cheer which he and all the members of his party supplied. It was a rare pleasure to have Professor Lewis in our expedition. The presence of Director Abbot and Mr. Moore, of the Smithsonian Institution Expedition, was at all times a happy arrangement. It was a great satisfaction to every member of our party that Mr. Abbot's scientific plans were carried out exactly as planned. I gladly acknowledge the able assistance of my colleagues, Messrs. Pehhine, Aitkex, and Albrecht, whose services were always available, both in the preparations and at the station. It has been the lot of Dr. Perrine and myself to be associated in the observation of three eclipses. A veteran of five eclipses, he has no superior as an eclipse observer; and his services, placed unreservedly at my command, were held in high esteem. A BOLOMETRIC STUDY OF THE SOLAR CORONA By C. G, Abbot. The Smithsonian Institution was represented among ob- servers of the eclipse of January 3, 1908, by a small expedition including the writer and Mr. A. F. Moore, of Los .Ajigeles. Our charges were defrayed by the Institution, but we went by invitation and with the co-operation of Director Campbell, of the Lick Observatory, and shared in the benefits of the careful provision which he made for the general welfare and success. We proposed to measure, with that extremely sensitive elec- trical thermometer called the bolometer, the intensity of the radiation of the solar corona, and to determine the quality of coronal light as compared with sunlight. I ■ • .'} M, ..u. I J 11- . 1 Ai-V' /- ^ 1.-1 astronomical ooctety of tfie Facipc. 07 In the year 1900 the first bolometric observations of the corona were made by Smithsonian observers. From these observations it was inferred that, as regards quaHty, the radia- tion of the inner corona was far richer than that reflected from the Moon in visible light. In view of this consideration and others, the inferences drawn by the writer from the bolometric study of the corona made in 1900 were unfavorable to the view that the radiation of the inner corona is produced mainly by the incandescence of matter heated to high temperatures by reason of its proximity to the Sun. The bolometric obser- vations at Flint Island were designed to test the inferences above referred to and to measure more definitely the quantity and quality of the coronal radiation. APPARATUS. Referring to the accompanying illustration, a concave mirror of so"^"" diameter and only loo''" focus, mounted equatorially and driven by a clock, served to produce a very intense image of the corona. A small guiding telescope was attached to the mirror frame so that the observer might point toward any desired object. In the focus of the mirror was placed the bolometer. A glass plate 3"" thick was fixed close to the bolometer, between it and the mirror, so that the radiation examined was thereby limited to wave-lengths less than about 3;i. About 10™ in front of the bolometer was a blackened metal shutter, which cut off the beam except when designedly opened. The opening of this shutter, therefore, exposed the central part of the bolometer to such rays as are transmissible by glass. Between the shutter and the glass plate, and close to the latter, was a special screen composed of a thin stratum- of asphaltum varnish laid on one side of a plane parallel glass plate 3°™ thick. This screen was held out of the beam by a spring, except when designedly interposed. Its property, when used, was to cut off nearly all the visible part of the radiation, while transmitting nearly all of the infra-red rays transmissi- ble by glass. By interposing this absorbing screen the pro- portion of the observed radiation which lay in the infra-red spectrum could be roughly determined. The equatorial was set up at Flint Island on the beach at about 12™ distance from the galvanometer used for observing the indications of the bolometer. Two galvanometers were provided, exactly alike in resistance and general construction, and arranged so that if at the last moment any accident should happen to one the observer might pass at once to the other.' A thatched hut. shaded by palm trees, sheltered the gal- vanometers and their appliances, and was found to give most satisfactory protection both from heat and rain. During the eclipse a rise of temperature of one bolometer strip of about o* .000,01 C. would have produced i"™ deflection of the gal- vanometer. It is possible to detect temperature changes of O°.ooo,ooo,oi C. with the bolometer, under special conditions, but the sensitiveness employed was regarded as good for a temporary installation. THE OBSERVATIONS. The approach of totality was uncommonly exciting on this occasion. Early in the morning the sky was overcast with thin high clouds, but these gradually grew thinner, so that after 9 a. m. the prospects indicated a streaky sky, containing something almost too thick for haze, but almost too thin for cirrus clouds. These prospects were fulfilled exactly during totality, but in the quarter of an hour next preceding a thick cloud caiTie up, rain fell fast from 11'' 8" to 11" 14", and the sky became clear of the low cloud only fifteen seconds before totality at the Smithsonian station. The rapid change from fair prospects to completely discouraging ones, and the return to good conditions just at the critical time, will long be remembered. Our entire immunity from rain during totality was due to the fact that our station was about one thousand feet north of the one occupied by the Lick Observatory. The intensity and quality of sunlight was determined within twenty-five minutes of totality, both before and after, and dur- ing totality measurements were made at five different regions ■of the corona and on the dark Moon, A general summary of the results of these and other observations follows : — 'This prudenl mesiure wr> suggested bjr Mrs, A>i Astronomical Society of the Pacific. 89 INTENSITY OF RAYS (OBSEEVED THROUGH GLASS). InleniitT for unit Source. angnlar no. Sun near zenith, Flint Island 10,000,000 Sky 20° from Sun, Flint Island. . , . 140 Sky far from Sun, Flint Island. ... 31 Sky average, Flint Island 62 Sky average, Mt. Wilson, Cal 15 Moon at night. Flint Island 12C?) Moon during eclipse, Flint Island.. o Corona i/io radius from Sun 13 Corona 1/4 radius from Sun 4 Corona 3/4 radius from Sun o PROPORTION OF RAYS WHICH ASPHALTUM TRANSMITS. Delerminalion. Mi^aa Source. I. II. (WeigbWd). Sun 3/10 radius from limb. . 0.333 0.331 0.332 Corona i/io radius from limb 0.343 0.384 0.364 Corona 1/4 radius from limb 0.387 0.323' 0.362 Moon at night 0.5 Sky, zenith day .... 0.23 DISCUSSION OF THE RESULTS. When we recall the extreme brightness of the sky within a single degree of the Sun, as compared with that 20° away, and consider also the figures just given, it seems very unlikely that the corona \vill ever be observed without an eclipse. The nature of the radiation of the inner corona has been supposed by some to be principally reflected solar radiation, by others to be principally due to the incandescence of particles heated by reason of their proximity to the Sun, by others to be principally luminescence perhaps similar to the Aurora, and by some as a combination of all of these kinds of radiation. The spectrum of the corona is mainly continuous, but has some inconspicuous bright lines, and in its outer part has dark solar lines. Undoubtedly there is sunlight reflected by the matter of the corona, and no less surely the corona must be hot. As for the idea of luminescence by electrical discharge, though the streamers of the corona are a reminder of the Aurora, one hesitates to recommend an explanation involving 23niA.M. I First Quarter... June 6, 8" 56" P.m. FullMoon ■■ 15, 8 32 p.m. Full Moon " 14, 5 SS *-»•■ Last Quarter. . . " 22, 4 17 p.m. Last Quarter.. . " 30, g 26 p.m. New Moon "29,7 14 p.m. I New Moon " 28, 8 31 a.m. There will be an annular eclipse of the Sun on June 28th, which will be visible as a partial eclipse throughout the United States. The path of central eclipse begins in the Pacific Ocean, passes through Mexico and southern Florida, across the Atlantic, and ends in Africa. The annular eclipse of the Sun does not compare in interest to the total eclipse, as the disk of the Sun is at no time completely covered, and there is therefore no opportunity for study of the corona and other outer layers of the Sun's atmosphere, which do not come into good view except when the part of the Sun ordinarily visible is completely hidden by the Moon. The Sun reaches the summer solstice and summer begins on June 21st, at noon, Pacific time. Mercury passes superior conjunction and becomes an even- ing star on May 7th. It reaches greatest east elongation, 23° 59', on June 7th, and reaches inferior conjunction on July 4th. From about the middle of May until after the middle of June it remains above the horizon more than an hour after sunset, and just about the time of greatest elongation, early in June, the interval is nearly two hours. For some weeks it may be seen in the evening twilight without difficulty. The num- ber of days when the planet is visible is much greater than at average greatest elongations. The greatest elongation, 23° 59', is somewhat above the average ; but the planet comes to its aphelion about two weeks after, and this prolongs the period between greatest elongation and inferior conjunction. This interval is twenty-eight days, a long one as compared with the sixteen days at the previous appearance of the planet in February. The relative motions of Mars and Mercury during June are interesting. Mars is moving rather steadily eastward and a little southward at the rate of about 42' per day. At the beginning of the month Mercury is about 4° west and north of Mars, and is moving in the same genera! direction, but at a considerably greater rate. It passes Mars on the morning of June 7th, the least distance between the planets being only 19'. But the speed of Mercury has been diminishing, and on the morning of June 17th Mars overtakes and passes Mercury. Between the two dates the planets are never much more than 1° apart. Mercury's eastward motion ceases on June 21st, and it then begins to retrograde. The same thing happens with Mercury and Neptune, the two planets being in conjunction twice, on June loth and on June 30th. Venus is an evening star and passed greatest east elonga- tion on April 26th, On May ist it remains above the horizon about four hours after sunset, nearly the maximum possible in our latitude. The interval diminishes, and on June ist it is only three hours. During June it diminishes with still greater rapidity, and at the end of the month it is only a little more than a quarter of an hour. The planet will reach Inferior conjunction with the Sun on July 5th. During the whole period the planet will be very bright, the maximum being reached on May 29th, a time midway between the dates of greatest elongation and inferior conjunction. For some weeks before and after the time of greatest brightness the planet will be brilliant enough to be seen in full daylight. Venus is in conjunction with Neptune on the morning of May 21st, and with Mars on June 22d, Mars is still an evening star, but the Sun is overtaking it in their common eastward motion, the distance between them diminishing from 37° to 18° during the two months' period. On May ist it sets about three hours-after sunset, and at the end of June only one hour after. It will not be easy to see toward the end of June, being so near the Sun, and also because it has nearly reached its minimum brightness. It will then be distant from the Earth about 240.000,000 miles, within 8,000,000 of the maximum distance. Jupiler is still in good position for observation in the west- ern sky in the evening. On May 1st it sets at about \^ a.m., and on June 30th at about g'' 30" p.m. During the two months' period it moves from Cancer to the western part of Lea, about 10° eastward and southward, and on June 30th it is about 12° west and north of Regulus, the brightest star in Leo, 1 /UfrottQmtcai aociely of the racipc. 93 Saturn is now a morning star, rising at a little before 4'' a.m. on May ist, and at about midnight on June 30th. It is rather too near the Sun to be at all conspicuous at the former date, but the distance grows greater rapidly, and it will soon be easy to see in the morning,twi light. During May and June it moves 6° eastward and 2° northward in the constellation Pisces, During the spring months the Earth has been moving farther away from the plane of the rings, and the apparent minor axis has therefore been increasing, so that at the end of June it is about one seventh the major axis, and about one third of the diameter of the ball of the planet. A small telescope will now show the rings easily. Uranus rises at about midnight on May ist, and very shortly after simset on June 30th. It remains in Sagittarius and moves about 2° westward in the two months' period. The nearest bright stars are the "milk-dipper" group, and the planet is about 5° north and east of the nearest one. Neptune is in the western sky in the evening. It is in the constellation Gemini, and by the end of June has nearly reached conjunction with the Sun. (SIXTY-THIRD) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to J. Grigg, Esq., Thames, New Zealand, for his discovery of an unexpected comet on April 9, 1907. Committee on the Comet-Medal : W. W. Campbell, C. D. Pehrine, San Francisco, March 26, 1908- ChaS. BurckHalteR. (SIXTY-FOURTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the .^stronomical Society of the Pacific has been awarded to Mr. J. E. Mellish, Madison, Wisconsin, for his discovery of an unexpected comet on October 13, 1907. Committee on the Comet-Medal: W. W. Campbell, C. D. Perrine, San Francisco, March 26, 1908, Chas. Burckhalter. NOTES FROM PACIFIC COAST OBSERVATORIES. On the Reseau. In my paper on "The Distortions of Photographic Films on Glass'" appeared, as No. 6 in the summary of results, the fol- lowing paragraph :■ — 6, If the results obtained in this investigation for small plates be found to apply with equal force to larger plates, it will follow that the assumption which is the basis for the use of the reseau is not well founded. The assumptions involved, briefly staled, are as follows : First, general distortions exist; second, they differ in different parts of the plate; third, they may be assumed to be linear within the squares of the reseau, i. c., over a stretch of 5""" or more. The supposed advantages of the assumptions. If the resea ing of the labor involved the reseau- lines and in th the method of referring all the n entirely upon the validity of these thre I can be dispensed with there will be a sav in making the large number of settings o reductions of the In regard to this pnrafrraph, I have had an interesting cor- respondence with Mr. HiNKS, chief assistant in the observa- tory of Cambridge University. The subject appears to Mr. HiNKs and me to be of sufficient general interest to warrant the publication of the principal points that were brought out by the discussion. Mr. Hinks agrees completely with my results on the nature and magnitude of the distortions in the gelatine film, the discussion being simply upon the question of the advisability of contimiing to use the reseau, even though the original cause for its introduction has been shown to be non-existent. The present reason for continuing the use of the reseau is one of convenience purely. With the exception of a foot-note to Mr. Hinks's second letter, I shall confine my- self to quotations from the correspondence. S. Albrecht, Df tki A. S. P.. VOL Pubhcattons of the Astronomtcal Society, < Mr. HiNKs's letter of August i6, 1907: — Permit me to say that I have been much interested in your dis- cussion of the distortion of the gelatine film in L. 0. SulUlin. No. II8. Your resnlls for the absohite distortion are very much of the same order as those which I hnve foimd on my own plates, and I entirely agree with you that the general distortion is quite small as a rule. Your result that the treatment of the plates by various methods makes practically no difference is very interestinE, valuable, and satisfactory. With your last result, Summary ! 6, I cannot however agree. It is true that the reseau was devised to eliminate distortion of the fUin, but it has proved itself so useful in other ways that it is still advisable 10 use it, even if it were absolutely certain that no distortion of the film exists. I would submit to you the following argument : If you do not use a reseau you must either use long screws or refer the meas- ures to scales. Now long screws wear out quickly, are tedious to work with, have temperature errors, and so on. On the other hand, it you use divided scales you have to make as many settings as on the reseau, and you do so at great mechanical disadvantage. Therefore from a purely mechanical point of view 1 consider the reseau is the best. Moreover it has in ils favor one great practical advantage — there is no need to worry about the plate being disturbed during measure- ment— it does not matter in the least. -And if for any reason you sus- pect an error in the measures, it is the easiest thing possible to put back the plate and measure up that image in a couple of minutes. Here we have several people using the same measuring machine. We divide up the day roughly among us, but any man is al liberty to remove another man's plate if he finds the machine not actually at work and wants to u^e it himself. You can't do that unless you have a reseau, and it is the greatest possible convenience to be able to have this rough and re.idy rule. From my letter to Mr. Hinks, September 30, 1907: — ... In regard to the distortions we are in perfect accord. As to the reseau there seems to be some difference of opinion due, I believe, to an imperfect understanding of each other's method of measurement. Especially the following sentence I did not understand ; "On the other hand, if you use divided .'scales you have to make as many settings as on the reseau, and you do so at great mechanical disadvantage." . . . I agree with you that long screits are out of the question. Metal scales also have a drawback. Glass scales, however, have a number of points in their favor, an important one of which is the fact that they have Ihe same coefficient of expansion as the photographic plate. Ouf Stackpole measuring machine has two glass scales, one for each coordi- nate, tlie distance between two successive rulings being 0,001 inch. The ; of the scale divisions have been carefully determined and are praclically negligible. In measuring, ihe frame, which carries the net- ting microscope and the two scale microscopes, is moved on slides parallel to the x and y coordinates (the j^'-shde is on this frame and carries the setting microscope and one ot the scale microscopes) unlil the intersection of two fixed wires in Ihe setting microscope falls over the center of the star image. The scales are then read off directly in the scale microscopes, the interval between the nearest scale division and the fixed wire in the scale microscope being estimated to the near- est tenth. Thus no micrometers are used for malting settings on the scale divisions. One of the disadvantages of the Stackpole machine is ttiaC it is not tilted, so that a person must stand stooped over it while measuring. In a differently designed machine this could be remedied, Ihe scale microscopes could be more conveniently placed, and it might be an advantage to have the inicnal between scale divisions o.oi"" instead of o.oor inch (0.025""" ±). As I imderstand it, for some unaccoiLntable reason the reseau docs not always reproduce itself exactly on the photographic plate, so thai it is not entirely reliable where the greatest accuracy is desired. , . , For somewhat more approximate [less accurate] measures I will grant that the resean has the advantage of a slightly greater speed, in that you read off the distances to the reseau-lines in the same micro- scope that is used tor setting on the star. When you want greater accuracy of measurement, you will probably have to use micrometers for measuring the distances to the reseau-lines. In our way of using the scales, the scale divisions from which we take our readings are always very close to the optical axis of Ihe microscopes. If for any reason you should wish to remeasure an image, the reseau certainly would allow it to be done quickly. As a matter of fact, how- ever, the direct and reverse settings give a check to the measures, and this check is always made before removing the plate. -^^m From Mr. Hinks's second letter, November 20, 1907: — ... I shall try to put briefly my explanations of the way I look aX the points mentioned in your letter. I. Some misunderstanding was caused by my ignorance of the Stack- pole machine, which I have never seen described. I did not know that you estimated on ten scales to o.oooi inch ( = 0.0025"""). I always sup- posed that you measurements went to a somewhat higher degree of apparent precision, which would almost necessitate your using micriv scopes to subdivide the scale. On our machine we measure to 0.0005™™ • and though we can't swear to the last figure exactly, I think wc can. on n good object, be accurate to within a probable error of about I unit in the last place. I imagine that the p. e. of one ot your estimates is very much the same,— that is. one unit of your last place, which is big- ger than ours (xs). Have you investigated your personal scale — i. e. preference for 5 over 4 or 6 for example? that is often a serious 97 reason why estimated last places should be in units as small as possible.' 3. The "mechanical disadvantage" to which I referred is involved in the fact tliat in your type of machine you depend upon perfect straightness of the main slides. If you use a reseau the slides may be practically as bad as they like. 3. The fact of uniformity of coefficient of e.tpansion is a strong' argument for glass over metal, but does not affect the question Rtseait Of not, as far as I can see. 4. The resemt does not reproduce itself exactly, but the so-called "errors of projection" are pretty constant. This means that you must stiidy the division errors of the copies — and study so many that the dis- tortion of the film in each goes out in the mean. This of course is tire- some. But after all. the projection errors are not so large as the residual distortions of the gelatine you are prepared to admit. And as they are more nearly constant, and thus unimportant in much refined work such as stellar parallax, where absolute places are unimportant, I think the advantage still lies with the reseau. 5. . . . Optical distortion of the microscope does not come in if you work with a suitable objective of the first class. ... A more frequent source of error in good machines is lilt of the icale in the eye-piece 1 But thai is fortunately eliminated on reversal. . . , Lectl'hks at Berkeley. The following course of lectures was given this term by members of the Lick Observatory staff before the class in Modem Astronomy at the University of California: — Professor R. H. Tucker— Tuesday, March 24th, and Thurs- day, March 26th. Subject, "Meridian Circle Work." Professor R. G. Aitken— Tuesday, March 31st; subject, "The Rings of Saturn." Thursday, April 2d; subject, "On Double Stars." Professor C. D. Perbine — Tuesday, April 14th, and Thurs- day, April i6th. Subject, "The Lick Observatory Crocker Eclipse Expedition to FUnt Island to Observe the Solar Eclipse of January 3, 1908." A. O. Leuschner. e Siscfcpele nucbine Ihe probable errur of a position, for a good objcc Intervil bciw«n REPORTS OF OBSERVATORIES.' CHAMBEELIN OBSERVATORY. DENVER, COLORADO. During the year 1907 Mr. D. Shelton Swan and the director of the observatory made observations of comets and of Ih. planet £™. jj^ i^ ^^^^ Directs. INTERNATIONAL LATITUDE OBSERVATORY, URIAH, CALIFOKNIA, Regular observation for the variation of latitude was con- tinued throughout 1907, according to the programme assigned by the International Geodetic Association. Doctor S. D. TowNLEY was succeeded in charge September 1st by the writer. A comparison of over five hundred of the 835 separate determinations of the latitude made between June 13th and August 30th, about half by each observer, showed practically no difference of personal equation. The probable error of a single determination was found to be about o".io for each observer. The weather was in general favorable, till the later months of the year, when there was an abnormal prevalence of clouds. The longest interval without observations was twelve nights. December ist to 12th, due to almost continuous cloudy weather: there were two intervals of seven days, due to unfavorable weather, in the first quarter of the year. The following table gives a summary of the observations for the variation of latitude. The columns contain, respectively, the number of determinations made each month, the number of nights on which observations were made, the number of complete nights (sixteen determinations), and the greatest in- terval in each month during which no measures were ob- tained : — ged alphabeticBllj » 19D7. Piiia. NighU. NighlL Njghii. January 152 11 7 6 February March 147 12 7 7 April 209 IS 10 4 May 180 15 10 5 June 231 17 13 4 July 356 24 20 2 August 303 21 13 2 September 178 13 5 3 October 146 12 2 5 November 167 12 5 6 December 68 5 i 12 Totals 2,295 169 loi Means 191 14 8 -f- 5 -f- Seven determinations of the constants of the zenith telescope, well distributed in time, indicate very satisfactory stability throughout the year. j^^^.^ p Maddrill, Astronomer-iti-Charge. LICK OBSERVATORY, MOUNT HAMILTON, CALIFORNIA. (The report will be printed in the next number of the Publications.) LOWELL OBSERVATORY, FLAGSTAFF. ARIZONA, The work of the observatory for the past year includes : ( i ) Visual and photographic observations of the planets I'enus, Mars, Jupiter, and Saturn: (2) The visual and photographic observations on Afan made by the South American expedi- tion ; (3) Spectrographic work on the planets with especial reference to the lower red end of the spectra for investigations on atmospheric absoq^tion effects; studies in detail of the spectnim of Mars and of different parts of the disk of Jupiter; I4) Radial velocity determinations of a selected list of stars; (5) Charting of star-fields along the ecliptic with the Brashear doublet, and the discovery of eleven new asteroids, the deter- mination of their positions as well as the positions of a large number of known asteroids; (6) Micrometric measures of double stars; (7) Many laboratory visual experiments with reference to testing the validity of certain visual observations ^iidftSW^ *^ Publications of the on the planets; (8) Photographic experiments with regard to applications in planetary photography and the photography of spectra ; (9) Work on the improvement of methods and equip- ment for use in planetary photography. A more detailed ac- count of the above follows. Visual observations on Mars were begun here on March 22d and continued until January, 1908. The opposition of the planet just past was one of the so-called favorable ones. _The great southern declination of the planet, however, rendered it difficult for most observatories in the northern hemisphere. The more southern latitude of Flagstaff was here to its advan- tage. In spite of the low altitude of the planet, the outcome of the observations there, both visual and photographic, were very successful. The two most important results were (i) the observations on the two polar caps at their simultaneous maximum and minimum states respectively, their subsequent careers, and the addition to the knowledge of them in conse- quence; and, (2) the detection of a canal system connecting with the south polar cap analogous to that already detected for the northern. This was an especially telling contribution, as it confirmed the theory of the office and behavior of the canals previously advanced here. At the suggestion of Professor Todd, the Director decided to send an expedition to South America in his charge, and Mr. E. C. Slipheh was detailed by the Director for the Mars work. Planetary camera, amplifying lenses, color filters, and plates were made for him, the duplicates of those used in the work at Flagstaff. The party sailed from New York on May i ith, and arrived at Iquique, Chih, June 14th. The observing sta- tion selected, Alanza, was about sixty miles inland southeast from Iquique, in the desert Tarapaca, at an altitude of about four thousand feet. The excellent quality of both photographs and drawings shows that the expedition was very fortunate in finding at the first trial a locality with conditions so favorable for their work. Much credit is due to all the members of the expedition for the part they contributed to making the under- taking a success, and especially must great praise be given to Mr. Slipher for his part in the work. All the Mars observa- tions were made by him, and the excellent series of drawings and photographs he returned with testified to his ability and industry in carrying out the programme of work planned. ^stronomtcal Hoctety of Mention must also be made of the efficient assistance rendered him by Mr, A. G. Ilse, who was ktnd]y detailed by the Alvan Qark & Sons Corporation to be the mechanician of the ex- pedition. The photography of Mars was begun at Flagstaff on June 3d and continued until September 2d. Photographs were made by Mr. Lampland and the Director, and in all a little over five thousand images were made. At the South American station, photographs were made by Mr. Slipher from June Z4th until August ist. Actual count since his return shows that he had made over 13,300 exposures. The South American photographs are, on the whole, superior, though a large per cent of the images of both series have excellent definition. In ■ 1907 the larger and brighter disk of the planet, more efficient camera equipment devised by Mr. Lampland, and the value of experience in the work, ail contributed to obtaining better photographs than those made during the opposition of 1905. The length of time covered by the present series and the uni- formly good quality of the images make them of great value, not only as a corroboration of the drawings, but also for study independent of the visual results. The photographs show an amount of delicate detail that is truly remarkable, and their importance and value in the advancement of Martian study can best be fully appreciated by any one who has spent much time and care. in charting visually the difficult detail of the planet. Detail that taxed vision to the utmost, especially mark- ings in regions lacking in or having slight differences of con- trast, could sometimes be seen with ease in the negatives made at the same time. These results bring out well the efficiency of the photographic plate, with suitable exposure and develop- ment, in registering delicate detail and small variations in contrast. Generally the photographs bring out the detail in the dark regions better, compared with the appearance of the planet visually, than in the light regions, and the negative here seems to be superior to the eye in detecting small differences of con- trast. Of course, for form, fineness, or linearity, the eye is first. Some idea of the delicacy of the detail photographed may be gathered from the fact that the twin canals Gihon and Eu- phrates were shown double in many of the images, made at different dates, of both the South American and the Flagstaff photographs. I I I02 fubltcatxons of The series of measures by Mr, Lampland and the Director, for the determination of the position of the axis of Mars and the eccentricity of the south polar cap, have been reduced and entirely confirm the lesser obliquity of the Martian ecliptic, found from the earlier Flagstaff measures, 1901-1905. (See Lou'ell Observatory Bulletin. Nos. 9 and 24.) This show* that the change in the obliquity suggested by the writer, and now incorporated in the ephemeris of the "British Nautical Almanac," was in the right direction. Observations on Venus were made by the Director during the summer months, confirming his detection of the markings upon it in 1896-7 and 1903, and have been continued by Mr. E. C. Slipher since November. Iiipiler was observed during April and May. A good series of drawings and a number of photographs were made. The wisps crossing the equatorial belt, so well shown in the draw- ings of Mr. ScRivEN Bolton, of England, were easily seen, and also confirmed by photographs. Observations were made on Saturn in June and from the first of November until January. A little before sunrise on June 19th, a new phenomenon was detected here in the ring system. The most conspicuous feature of the disk at the time was the dark band, the shadow of the rings, which then belted the planet's equator. The shadow, far from being dark, was only moderately dusky, and furthermore presented, when first looked at, a curious tripartite appearance. On more careful scrutiny its lack of uniformity proved to be due to a narrow black line that threaded it medially throughout its length, the black core being perhaps one fourth as wide as the less dense background upon which it stood. At the same time, the rings themselves could with attention he made out as the finest knife-edges of light cutting the blue of space on either side of the planet's disk. The planet was not looked at again until October 31st, other work occupying the observatory in the meantime. In November, however, it was critically studied. The dusky band was evident, as in June, and the black line made core to it, as before. This black medial line was by no means even ; it both undulated slightly and showed irregulari- ties of outline, one black bead in especial being noticeable upon it about half way from the planet's center to its (the Astronomical Society of the Pacific. 103 planet's) eastern limb. (November 13, 7''. M. S. T.) The line also seemed not quite central in the belt, but a little nearer its northern edge. In November the rings were easily seen, although, as before, only the edge of their plane was presented to the eye. But in addition to the genera! line of their light, agglomerations were plainly discernible on them. A number of measures of the agglomerations and the core of the shadow- band were made in November and December. During the last part of December the agglomerations were too faint for meas- urement, and were last seen by Mr. Lampland on December 31st. The rings were glimpsed by him on January jd and 4th, but were then so faint that he was unable to see if irregulari- ties were still present. Unfavorable conditions prevented observations until January 7th, when the rings were easily seen and found to be perfectly continuous. An investigation by the writer, explaining the core of the shadow-band and the agglomerations in the ans.-e of the rings, has been published in detail elsewhere. A brief statement of the results of this study may be of interest here. The investigation brings out the interesting fact that the particles composing the ring- system cannot all be situated in one plane — that the rings are not flat rings but tores, rings after the manner of anchor-rings, encircling the planet. This out-of-planeness of the particles is easily seen, applying the methods of celestial mechanics, to be a consequence of the perturbing influence of the nearer satel- lites and the mutual impacts of the particles of the rings. In support of this view, we find that micrometric measures place the agglomerations where we should expect to find them from theoretical considerations. The black core of the shadow-band' leads to a like conclusion; that in the black core we are looking at such parts of the ring-system as are practically plane, chiefly ring A. and in the dusky shadow about it through particles, situated above and below that plane, lying in the other rings. The spectrographic work done during the year has been confined principally to studies of the red end of the spectra of the planets, and the radial velocity determinations of a selected list of stars. With greatly improved red-sensitive plates, per- fected by his extensive experiments with sensitizing dyes, Mr. Slipher has been able to photograph many hitherto unknown absorption bands and lines in the spectra of the major planets. y 104 Publications of the The lower red end of the spectra of the other planets and many stars are almost as interesting as those of the major planets. Of the new bands discovered in the spectra of the major planets, the strongest is found near X7200. This band in Jupiter and Saturn is far stronger than the characteristic one at k 6190. A series of plates of the spectra of Man and the Moon, photographed at equal altitudes, and under favorable conditions, on nights selected on account of their advantageous meteorological state, shows this band to be reinforced in the spectrum of Mars. The band A 7200 coincides in position and appearance with the "a" group of the telluric spectrum which Rowland and Jewell found to be due to water vapor. The D band is likewise broadened relatively with Mars spectra, indicating enforcement of the water-vapor lines there. A study has been made of the spectrum from different parts of the disk of Jupiter, revealing interesting differences. The results of these spectrographic studies will be published in the near future, A good deal of attention has been given to the problem of planetary photography, with a view to devising more efficient methods and equipment for that work. The planetary camera was rebuilt, according to designs by Mr. Lampland, during January and February, by Wm. Gaehtner & Co., of Chicago. In planetary photography, with a visual refractor, good color screens form a very important part of the equipment, and every effort has been made to obtain the best ones that could be made. Both solid (stained film of gelatine between plates of optical glass) and liquid (glass cell with plane -parallel walls containing the absorbing solution) filters have been used. Mr. R. J. Wall.^ce made three more solid filters, and adjusted the absorbing solution for two liquid-filter cells. The optical parts for the liquid filters were made by Mr. O. L. Petitdidieh, and were figured accurately plane. The absorption vahies of two of the solid filters and of one of the solutions for the liquid fihers were adjusted by Mr. Wallace according to specifica- tions based on investigations by the writer. Mr. Slipher's remarkable success in his experiments in sensitizing plates, with comparatively even sensitiveness for a long range of the spectrum extending far into the red, suggested that his plates might be used with good results in planetary photography in Astronomical Society of the Pacific. 105 connection with a suitable color-screen, by which more perfect monochromatization relatively to the amount of light forming the image might be attained. Tests of the plates in the pho- tography of the planet brought out that they lacked the quality of delicate gradation so important in this work. Later tests of the new filter, using Cramer's isochromatic plates, showed that it gave definition superior to the filters formerly used, though requiring a little longer exposure to give the same density of image. It proved indeed to have been previously made for use with these plates, though not for planetary photography. The investigation on the filters, giving a state- ment of the principles involved and the results of the experi- ments, will be found in Loivcli Observatory Bulletin, No. 31. Experiments were made with commercial photographic lenses (Zeiss and Cooke) for amplifying lenses in the planetary photography, but these were not found to perform as well as the new negative lens made by Mr. Lundin, of the Alvan Qark & Sons Corporation. In the laboratory visual experiments performed, in connec- tion with investigations on Mars, efforts have been made to carry them out under conditions as nearly like those found in actual observational work as possible. The 24-inch, 6-inch, and 4-inch telescopes, with different magnifications, have been used in the experiments. By varying the different factors, optical systems, apertures, and magnifications, and "seeing" (atmospheric disturbances) conditions existing in observing, work can be approximated quite satisfactorily. For instance, the effect of atmospheric disturbances caii be obtained by selecting certain moments for the observations, or by varying the length of the air-path, or the magnification. At the same time, one can of course vary the dimensions of the objects observed until they have the required angular dimensions. The optical systems and general conditions being about the same as in actual observing work, conclusions can more safely be drawn from the experimental work. Other additions to the equipment than those already men- tioned were, a new device for illumination of the field and improved electric illumination of the micrometer of the 24-inch telescope, and a large observing chair of the same pattern as the one used at the Ladd Observatory. Percival Lowell, Director. lo6 Publications ^of the NAVAL OBSERVATORY. MARE ISLAND, CALIFORNIA. During the past year the work of this observatory has been about the same as in past years. The number of chronometers rated and issued to ships has, however, somewhat increased, owing to the increased naval activities in the Pacific. The time service has continued as heretofore, and wireless mes- sages have been installed for giving the time to the fleet at Magdalena Bay, Lower California. These messages cannot be sent great distances by day, and at present are delivered on Mondays and Thursdays of each week, at 9 o'clock at night. This service has proved satisfactory. In some cases messages have been delivered to ships near Honoluhi, at a distance of fifteen hundred miles from the transmitting station. In addition to the routine work of the observatory as regu- larly carried on. the officer in charge has continued his re- searches on "The Cause of Earthquakes and Mountain Forma- "tion." Three papers on this subject have been published in the Proceedings of the American Philosophical Society at Philadelphia. The new theory, that these disturbances are due to the secular leakage of the ocean bottoms, may now be regarded as proved. The subject thus ojiened up, however, is still so unexplored that a fourth paper is to be added to those already published, in order to render the theory more complete. Recently the officer in charge has taken up a general revision of the orbits of double stars. Ten orbits, mostly of new pairs, have recently been communicated to the Royal Astronomical Society in London. The earthquake researches, which proved so fruitful of discovery in the domain of the physics of the Earth, were the natural outcome of the previous work on the internal constitution of the Sun and planets carried out here in 1904 and 1905. and published in the Astronomische Nach- richten. When the great earthquake occurred it was felt to be a public duty to seek out the cause of such disturbances, in the hope of ascertaining the relative safety of California. This region is now shown to be much less endangered than most regions about the Pacific Ocean. TIT See Professor of Mathematics, U. S. Navy, in charge of the Observatory. Astronomical Society of the Pacific. 107 SOLAR OnSERVATOBY OF THE CARNEfilE INSTITUTION OF WASHIXOTON, MT. WILSON, CALIFORNIA. The investigations in progress during the past year include : 1. Daily photography of the Sun with the photohelio- graph. 2. Daily photography of the Sun with the spectroheHo- graph. 3. Photography of the spectra of sun-spots. 4. Photographic comparisons of the spectra of various parts of the Sun's disk. 5. Spectrograph ic investi{,'ations of the solar rotation. 6. Laboratory investigations. 7. Pyrheliometric observations. Direct photographs of the Sun have been made daily with the Snow telescope, by Mr. Ellehman or Mr. Olmsted. These negatives are used mainly for comparison with spectro- heliograph plates. The daily series of photographs made by Mr. Ellerman or Mr. Olmstkd, with the 5-foot spectroheliograph and Snow telescope, comprises negatives made in the early morning and late afternoon, with the lines of calcium, hydrogen, and iron. The hydrogen line regularly employed is H8. We have re- cently discovered, however, that the Ha line gives results differing very decidedly from those obtained with Hh. The high sensitiveness for red light imparted to photographic plates by bathing them in a three-dye solution, devised by Mr. Wallace, of the Yerkes Observatory, permits excellent photo- graphs to be made with the Ha line, in spite of the compara- tively low dispersion in the red of the 5-foot spectroheliograph, and the consequent necessity of using a very narrow camera slit. Hereafter Ha plates will be taken regularly, since the bright flocculi which they bring out are sometimes, if not invariably, absent from the H& plates. There also seem to be interesting differences in the forms of the dark flocculi shown by the two lines. These results have only just been obtained, and it has not yet been possible to ascertain the causes which produce the interesting and striking differences revealed by the photographs. The 30-foot spectroheliograph of the tower telescope is under construction and should be in use within a few months. io8 Publications of the Some experiments have been made, however, with the 30-foot Liltrow spectrograph of the tower telescope used as a spec- troheliograph. The 12-inch object-glass, of sixty feet focal length, of this telescope, is mounted in a carriage and con- nected with an electric motor in such a way that it can be moved at a uniform rate in an east-and-west direction. This causes the image of the Sun, formed in a house at the base of the tower, to move across the collimator slit of the spectro- graph. Most of the work has been done in the second-order spectmm of a 4-inch plane grating, which is not nearly large enough for the fu!l aperture (six inches) of the spectrograph, but is nevertheless better suited for this purpose than any other grating in our possession. The spectroheliograph attachment consists of a plate-carrier movable on steel balls across two adjustable slits. This apparatus is mounted on the spectro- graph in the position usually occupied by the plate-holder employed for photographing spectra. The two slits are made to coincide with any two lines of the spectrum, and the photo- graphic plate is moved over them at the same rate as the solar image — by means of the same motor. In this way monochro- matic images of limited regions of the Sun can be photo- graphed simultaneously with two of the Fraunhofer lines. With this apparatus the peculiirities of the Ha lines were discovered. Experiments are now in progress with other dark lines. A s[jecial attempt will be made with this instrument, and with the permanent 30-foot spectroheliograph, to determine whether anomalous dispersion phenomena are exhibited by the flocculi. The photographic study of the spectra of sun-spots, which was mentioned in the last annual report, has been continued and extended through the advantages afforded by the new tower telescope. The negatives of spot spectra made with the 18-foot Littrow spectrograph and Snow telescope have been used for a preliminary photographic map of the spot spectmm, extending from X4600 to A 7200. The map consists of twenty-.=ix strips, each including one hundred Angstroms, and is provided with a solar spectrum for comparison purposes and an approximate scale to aid in the identification of spot lines. At the recent Paris meeting of the International Union for Cooperation in Solar Research this map was adopted for the use of the cooperating observers. Each visual observer.jl Astronomical Society of the Pacific. 109 selected a certain limited region of the spot spectrum, in which he compares the lines, as seen at the telescope, with those recorded on the map. In this way any changes in the relative intensities of the lines, if such occur, can be readily detected. Copies of the map have been placed in the hands of all observ- ers who are taking part in this work of the Solar Union. A preliminary catalogue of the lines affected in sun-spots is being prepared by Mr. Adams and myself, with the assistance of Miss Bi'RWELL. of the Computing Division. The first install- ment of this catalogue, prepared by Mr. Adams, covers the region A 4000 to A. 4500, and contains about 875 lines. The publication of the second portion of the catalogue, covering the region from A 4500 to A 5000, has been delayed by the fact that the photographs of spot spectra, made with the 30-foot spectrograph and the tower telescope, show many more lines than our previous photographs. These plates are there- fore being used in preference to the earlier ones in preparing the catalogue. They will also serve to give a definitive map of the spot spectrum on a scale of 4""" to an Angstrom, Special apparatus for enlarging and widening the spectra for this map is now under construction and will soon be ready for use. The hypothesis that the relative intensities of the spot lines are due to reduced temperature has received further confirma- tion during the year, especially through the identification in the spot spectrum of many bands due to compounds. This work is referred to below in connection with other laboratory inves- tigations. A photographic study of the spectra of various parts of the Sun. miide by Mr, Adams and myself, has shown that marked differences distinguish the spectrum of the center from that of points very near the limb. The Fraunhofer lines not only undergo changes of intensity, similar to those observed in the case of sun-spots, but they are also shifted in many instances from their normal positions. Since the lines of the cyanogen flutings are not shifted, and since the relative displacements of various metallic lines correspond fairly well with their displacements produced by pressure in the laboratory, it seems probable that the changes in line positions are due to an increase of effective pressure near the limb. Such a conclu- sion would be in agreement with the views of Hae-.m, How- Publications of the ected to turn out as nearly as pos- sible "haphazard," after eliminating the Sun's motion, Mr. Eddington finds that no value can be assigned to the solar motion which will make the outstanding motions of the stars consulted conform to pure chance. The curve of these "residuals." instead of having a single a^>ex, has two, It is as if the box just described had two holes at the top. He has "shown that the outstanding motions can be accounted for only on the hypothesis that the universe — i. e., of course, all the stars consulted— is composed of two groups. In each of his groups the internal motions of the stars composing the group practically completely conform to the required law. So each group can be regarded as an independent whole, while the total visible universe, by the same argument, can no longer be taken as a single entity. Thus we shall have now to speak of the relative motions of the three following items, — viz.. ( i1 the stars composing drift i taken as a whole; (2) the stars composing drift 2 taken as a whole; (3) the Sun." Atmospheric Absorption. — Extensive photometric observa- tions during the year 1906 led M, Nobdmann, of the Paris Publications of the /Astronomical Society, &c. I2l Observatory, and the late Director Lcewy to the remarkable conclusion that, though the absorption of sunlight by the Earth's atmosphere increases, with zenith distance, regularly and rapidly from the red to the violet, the absorption in the case of starlight is, on the contrary, much greater in the red and orange than in the blue and violet. Near the horizon, however, as was to be expected, dust and water vapor scatter the short waves more than the long, so that the absorption of starlight tends to the diurnal tj-pe beyond a zenith distance of about iio°.— Journal B. A. A,. Vol. XVIII, No. 4. Field Ulumination. — .\x\ improved method of illuminating the field in a transit instrument has recently been devised by Sir W, Christie, Astronomer Royal of England, and Mr. Harold Christie. It had been found that with the axis form of illumination apparatus, in which an adjustable annular reflector was employed, the apparent position of the wires was slightly changed by reversal of the telescope. By attach- ing the lamp, projecting lens, and reflector to the tube beyond the object-glass 'or fastening the reflector to the object-glass itsetfl, the discordance between time observations in the two positions of the telescope has been practically eliminated. In the improved form, the annular mirror is replaced by a cen- tral matt-surfaced disk, fixed at 45", and of sufficient size to avoid certain diffraction effects. The intensity of illumination is' regulated by a rheostat. This method of illumination is to be applied to several of the instruments at Greenwich. — Monthly Notices R. A. S., January, t^oS. The next meeting of the Astronomical and Astrophysical Society of America will be held at Piit-in-Bay Island, Lake Erie, on August 25th and succeeding days. Mr. Rich.*lRD Hinckley Allen, of Chatham, N. J., author of "Star Names and Their Meanings." and a life member of the Astronomical Society of the Pacific, died on January 14, 1008, at Northampton, Mass., of pneumonia following an attack of grippe. 122 Publications of the Astronomtcal Society, &e. M. Baillaud, director of the Toulouse Observatory, has been appointed director of the Paris Observatory, and M. BoiiBGET. adjunct astronomer at the Toulouse Observatory, has been appointed director of the Marseilles Observatorj'. 'The deatli is announced of Lieutenant- Colonel R. J. L Ellery, professor of astronomy and late director of the Melbourne Observatory, at the age of eighty years. The return of Encke's comet was observed by Dr. Wolf at Heidelberg, iqoS, January 2. It was afterwards found on a photograph taken at the same observatory, 1907. December 25. The correction to the ephemeris published in Astronomischc Kachrichten, No, 4222, was + 2'",4, — 24'. Mr. H. M. Parkhubst, an amateur astronomer of Brook- lyn, N. Y., who did a great deal of work in observing asteroids and variable stars, died January 21st, at the age of eighty-three years. Sir David Gill, late his Majesty's Astronomer at the Cape, enjoys the unusual honor of having twice received the gold medal of the Royal Astronomical Society. It was first pre- sented to him in 1882 for liis work in connection with the determination of the solar parallax, and last evening a second was awarded him in recognition of his contributions to the astronomy of the southern hemisphere. — Daily Telegraph, London. NEW PUBLICATIONS. Abnanaqite nautico para el aiio 1909, Calculado de orden de la Superioridad en el Institute y Observatorio de Marina de San Fernando. 1Q07. 4to. xi + 634 pp. Paper. Annals of Harvard College Observatory. Volume LX. 4to. Nebulie discovered at the Harvard College Observatory. No. VI. 47 pp. Double stars south of —30^. and of magnitude 6.3 to 7.0. No. VU. 4 pp. Annuario astronomico del iQO^. Publicato dal R, Osserva- torio di Torino. 1908. 8vo. gi pp. Paper. Anuario del Observatorio Astronomico Nacional de Tacubaya para el ano de 1908, 1907. i6mo. 580 pp. Paper. Astronomisch-geodatische Arbeiten in der Scbweiz. Zehnter Band. Ziirich. 1907. Folio, ix -+- 405 pp. Two plates. Paper, Bailey, Solon I. Peruvian meteorology. Observations made at the Arequipa Station, 1802-1895. Annals of the Astro- nomical Observatory of Harvard College. Vol. XLIX. Part I. Cambridge. Mass. 1907, 4to, 103 pp. Plate. Paper. Bailey, Solon I. A catalogue of bright clusters and nebula;. Annals of Harvard College Observatory. Vol. LX, No. Vni. 4to. 30 pp. Five plates. Paper. Bauschixgek, J, Genaherte Opposition s-Ephemeriden von 32 kleinen Planeten fiir 1908 Januar bis 1908 August, Ver- ofFentlichungen des Koniglichen Astronomischen Kechen- Instituts zu Beriin. No. 34. Berlin. 1908. 8vo. 12 pp. Paper. B0HI.IN, K.^RL. Uber die Gcgenseitige Verteilung der Pole der Doppelstembahnen der Milchstrasse, des Sonne n- systemes sowie des Andromeda-Nebels. Arkiv for Mate- matik, Astronomi och Fysik, utgifvet af K. Sven.ska Vetenskapsakademien i Stockholm. Band 3. No. ig. Uppsala and Stockholm. 1907. 8vo. 8 pp. Three plates. Paper. BoRCEN, C. Logarithmisch-trigonometrische Tafel auf 11 (bczw. 10) Stcllen. Publikation des .Astronomischen Ge- sellschaft. XXII. Leipzig. igo8. Folio, vi -i- 55 pp. Paper. 124 Bhester, a. Essai d'une explication d« niecanisme de la l>eriodicite dans le soleil et tes etoilcs rouges variables, \"erhandelingen der Koninklijke Akademie van Wcten- schappeii te Amsterdam. Deel IX, No. 6. Amsterdam. 1908. 4to. 137 pp. Paper. Bnlletin de I'Observatoire Populaire de Rouen. Annee 1907. Rouen. igo8. Svo, 87 pp. Paper, Canadian astronomical handbook for 1908. Published by the Royal Astronomical Societv of Canada. Toronto. 1907. i6mo. 93 pp. Paper. Comas Sol.4, J. Astronomia y ciencia general ; Coleccion de trabajos cieiitificos de popularization refcrentes a la astronomia, a la sismologia. a la htstoria de las ciencias en el siglo XIX, etc, Barcelona. 1907. 4to. 637 pp. Price, 6 pes. 50c. DoNiTCii, N. Observations de I'eclipse totale dc soleil du 29-30 Aout 1905, Bulletin de I'Acadeinie Iniperiale des Sciences de St. Pctersbourg. St. Petersbourg. 1907, 410, 28 pp. Four plates. Paper. Eiffel, G. Atlas metcorologique pour I'annee 1906. D'apres vingt-deux stations Frani;aises. Paris. 1907. Atlas form. Boards. Fr.'\ncos, Salvatxjr Garcia. Tablas para el calculo de eclipses de tos satelites de Jupiter. Observatorio de San Fernando. 1907. 4to. xi + 23 pp. Boards. King, Euwahd S. Standard tests of photographic plates. Annals of Harvard College Observatory. Vol. LIX, No. I. 4to. 32 pp. Plate. Paper. Kramer, Julius. Untersuchungen und Tafeln zur Theorie der kleinen Planeten von Hekubatypiis nebst abgekurzten Bewegungatafeln des Planeten (861 Seinele fiir die Jahre 19CX) bis 1951. Ahhandlungen der Koniglichen Gesell- schaft der Wissenschaften zn Gottingen. Mathematisch- Physikalische Klasse. Keue Folge. Band V, No. 3, Ber- lin. 1907. 4to. 154 pp. Paper. LoEWY et PuiSEUX. Sur I'origine des accidents du sol lunaire. Exirait des Comptes Rendus des seances de I'Academie des Sciences. Tome CXLIV. 4to. 6 pp. Paper. Stebbins, Joel. Photometric observations of double stars. University of Illinois Bulletin. Vol. IV, No. 25, Urbana. 1907. Svo. 58 pp. Paper. Price, 75 cents. Astronomical Society of the Pacific. 1 25 Whittaker, E. T. The theory of optical instruments. Pamphlet. 72 pp. Published by the Cambridge Univer- sity Press. 1907. Price, as. 6d. net. Note. — In compiling the above list of New Publications the sizes of books are given in accordance with the table used hy the Macmillan Company. As future compilations will be based upon this table, it is inserted here for reference. A book 1-4 inches {10 centimeters) tall is a 48mo. 4-5 inches (io-i2j^ cent.) tall is a 32mo. 5-6 inches (125^-15 cent.) tall is a 24mo. 6-7 inches (15-17,'/! cent.) tall is a i6mo. 7-8 inches (lyyi-io cent.) tall is a i2mo. S-io inches (20-25 cent.) tall is an 8vo. 10-12 inches (25-30 cent.) tall is a 4to. Larger sizes are folio. Minutes of the Meeting of the Board of Directors held AT THE Bohemian Club on March 28, 1908, AT 5 :30 P.M. President Cushinc presided. A quorum was present. The following resolmioti was adopted; — Riiolicd, That the sum df tif6.66. having been advanced by the Life .Member- ihip Fund to Ibe Bnice Medal Fund, (kc VdI. XI, p. ;S. January i8, iSqg,) be now refunded by the Utter fund to Ibe Life Membcrtbip Fund. The Secretary reported ihat the President had appointed the follow- Auditing: D. S. Richamson (Chairman), J. Costa, Frank V. CORMISH. Nominating: ]. D. Gauoway (Chairman), C. D. Pebrime, Bevkkly HODGHEAD, J. K. MOFFITT, OtIO VOS GELDniN. The following named persons were elected to membership : — W. 0. Owen U. S. Examiner of Surveys, Imperial, Cal. Robert JoNCKHEE»E...Roubaix. Nord. France. The following was elected a corresponding i Remeis-Slerntvarle, Bamberg, Germany. .Adjourned. OAiAem»T, C. E. HU/f ID rtw ■!■ iiimt*tn mcRiiaDCid. Tk* namPxr of Itanoho* Comcl- Ucdalt anrdet tn dale u tittftomi. Rapcdfallr nbafncil. Uirch (A, r«at. Astronomical Society of the Pacific. The Treasurer submitted his Annual Report, as follows: — Annu.m, Statement of the Receipts and Expenditures i AST1»N0M[CAL SOCIETV OF THE PaCIEIC EOK THE Fiscal Year Enoisg Makch z8, 1908. (inlereM) t 67 7J Sality Secrel»r7 Nowry snd Stall Rtni safe deposit igoS. Match iSth, BalancE *'73 "• LIFE MEMBERSHIP FUND. Leu inleresi transferred lo General Fun tgoB. March iBtti. Balance 67 7) i.795 « 67 73 Astronomical Society of the Pacific. Balancei ,» folic™ Wilh Donohoe Kelly Banking Compai.y Lift Mtmhmhit Fund. Wilh German Savingi ani4 Loan Society 1 South Pacifie Coa»t Railway Co, nt Mortgnge « per cent piiranleed (by S. P. Co.) ti.doo, Gold Bond No. uo6.. Clntemt Jan. and July; principal dne July. 1937.) V Librm Fund, Wilh Security Savingi Bank t S Oakland Transit Consolidated, tst consolidated Mortgage 5 per «nt Gold Bond No. .,31,8 ,.q tlntere.1 Jan. and July; principal due July. 193'-) Sun«?t Telephone and Telegraph Com 1, Si, 000 d Bond No, 6*1.. principal doe Oct.. 101 irinclpal due Jan., igi The Ediaon Electi r Company, nt eonsolidated Mortgage . Sinking Fund Cold Bond No. i6]6.. and Sept.: principal due Sept.. 1930.) n Dolbftr Fund. South Pacific Coasi . Railway Company, lit Mortgage 4 per (hy S. P. Co.). ti.ooo GoU Bond (Inlerest Jan. ai Id July: principal due July, 1937.) S per cent. tr,oo. (Inlerest Jan. ai id July: principal due July, 193a.) Bay Counties Powi J per cent, (..oo 0 Sinking Fund Gold Bond No. 1637.- (Interest March and Sept.; principal due Sept.. 1930.I The Ediion Electri ic Company. Lo. Angeles, rsl and Re- {on ding Mortgagi e 5 per cent. $i,doo Gold Bond No. i6q (Inlerest March and Septi principal dne Sept., r9»a-> 'fiBM Alrerd P««d. Sur«t Telephone cent. S1.000 r^ld Bond No. tijfi. and (Interest April and Ocl.: principal Hue Oct., 1929.) Contra CoKa Wal er Company, j per cent ti,Doo Gold Contra Costa Wal er Company, s per cent $1,000 Gold t Jan. and July; principal i D. S. RiCBAUMoa, J. COITA, The report was. on" F. R. ZiEL. Trt. Qtion, accepted and fUed. 130 Publications of the The Audiiitig Comtniltee siibmitled the following reporit- eanircr of Ihii Society for d«iog btg to report th»i Ihey tn -1 in the ra oma of T rent tirer Ziel on Ihe after- lake p all (ui <1> of Ihe Society .nrf -ve 1 0 er all hi> accou " with grea care. They roperly mted nr. The a1 HI visited he TBulU of Ihe M rcanlile Trim Tom pary. at +64 Calito mia Str« nd penion liy iospeneJ urilies of Ihe Saci ly then deposi finding paper* in ely guarded. ore reJuU of Iheir labor! Med with Ihe fact th« required or nduclirig ■ffiira of thii Society, ap d It it heit impre»ion that a) a butinw propoaltioo. ■ uU y should aiucli Id tJiai 0 Kce imporl nee of Ihe Crust. Very D. B. J. Co ly, R ClUltMOll. uililint C President CusHiNr. read an address in awarding the Bruce Medal for 1908 to Director E. C. Pickering, of Harvard College Observatory. After his address the President introdnced Director W. W. C.\mpbelI, of ihe Lick Observatory, who gave an interesting lecture rillnstralcd by lantern slidesl on "The Crocker Eclipse Expedition from the Lick Observatory. University of California, lo Flint Island." Adjourned. MiNUTF.S OF THE MeF.TINC OF THE BOARD OF DIRECTORS HELD M.\HCH 28, I90S, AT 10 P.M. The new Board of Directors met and chose Dr. chairman. .A quorum was present. The election of officers resulted as follows ; — President: Chables Bubckhai.teb. First Vice-Presidtnl: W. W. Campbell. Second Vice-President: G, E. Hale. Third Vice-President: F. Mor.se. Secretary: R. T. Crawford. Secretary fMt. Hamilionl : R, G. Aitken. Treasurer: ]. D. Galloway. Library Committee: Messrs, Crawkisd. Townlev, EIikaksoh. Comet-Medal Committee: Messrs, Campbell (ex-officio), Pesrine, ToWNLEY. The President appointed the following : — Finance Committee: C. S. Coshinc (Chai R. G. Aitken. L temporary d n), W. \\. CdocKER, Astronomical Society of the Pacific. 131 The President was authorized and instructed to appoint a of three to investigate and report to the Directors upon the matter of providing a rootn in San Francisco for ilie Society. Messrs, C S. CASHING, J. D. GALiowAY, and F. R. Ziel were appointed. The chairman of Ihe Publication Oainmittee was authorized to pro- vide stationery for the use of his committee. The Secretary was instructed to send a letter (to be signed by the President and the Secretary) expressing the appreciation of the Society of Ihe faithful work and long service of the retiring Director and Treasurer, Mr. F. R. Zibl. The Secretary was instructed to send a letter (to be signed by the President and Secretary) of thanks to Professor R, G. Aitken, the retiring chairman of the Publication Committee, for his long and excel- lent service on this committee. Adjourned. if^^PuDltcdtions of the Astronomical Society^^cT i OF THE SOCIETY. Mr. Ch*»i.es BficsHALTu Pritidm Mr. W. W. Cahp>eu Fira Vue-Pntidtia Mr. G. E. Haie Sicoiti yict-Pr,tidt*l Mr. F. MOUE Third yict-Prtiidm Mr. R. T. C«AWro»D CStudenti* ObKrvdory, BErkeley] Sfcrfwy Mr. R, G. AiiKEf. (Mount Hunllion, CI.) Stenlvf Mr. J. D. G*UMV/Ai Tnamrrt Fvr OiV(c/ori— AimiH, BoiicKHkLTEa, OursEu. Cxawfokd, CitociH*, Ccsamo. G«u.0WAr. Hah, Mom. Richauwm, TowRLir. H Financt Cvnimiltri — Mnuti. CusaiNC, Ckocxu, Aitxeh. ^^^^ CommilM «fl /■uAlirafioB— Miuri. Towsl.y. Masduu, Moow. ^^H I-iAriiry CommftfH—Melan. CiAwtasD, TowxuY, ElH>aH»r. ^^^H Cimtl-Midal Canimiliee—Mmn. CAiipi.t..L {ex-ofliiio), Pit«(rNt, Towhlet,^^^| The atlentiaii of new mcmberi ii called lo Aniele Vlll of the By-Law*, which only Subiequenl .nnml.pajmenls are due on Janua'ry m of eath 'tiucc^eJiSi u poHihli*"buM Mn" by^nSu llSuTd' Vdimled™ A«ronomiian'M«'' ™tht Pacific, Studeiiti' ObKrvalory. Berkeley. It u intended Ibal each member of the Society iball rcFiive > copy of each one Df (he PublUalioju for the year in which he wai elecleil la meinbcr>hip and (at all •ubwqucml yean. If there have been (unfortunately) any omiiiionl in Ibl) matter, it i> requeued that (he SecrcUriei be at once nolilied, in order that the milling nurnbera may be supplied. Membera are requeued to pTCKrve (he c«|net canlenll of ibe preceding number! will^alio be Kiit lo the mcHiberi. who can' then payment of two'ddUari pet volume lo either of the Seeretarle*. Any non-'mldeiil member within the United 5(atei can obtaio books from the Society*! Iibr*ry by aiadents' Ubiervalory. Berkeley. CaL. who will return tbe book and Om card. The Committee on Publication desire* lo say that tbe order in which oapen are printed in the />ub;icDIi'ofii is decided limply by convenience. In a ^neral Papen intended to be printed in a given number of the Publications sh''ould°be I'll of publication. It is not po!!ihle to »end proof iheels of papers to be printed lo viewB expreucd in the paper! printed, and for the form of their expreision, rou wilh the writers, and ii not asiumed by the Society itself. The tides of papeci far reading should be communicated to eilher of tbe Sec- tary in Berkeley will lend ' to any member of, the Society luilable !ta(ionety, prices include pMlage, and should be remitted by money-order or in U. S. posug* stamp!. The lendings are at (he ri!k of Ibe member. Tliosi member! who propoie to attend Ihe meelingii at Mount Hsoilton ilurial the !ummer should communicate with "The Secretary Astronomical SKiety ol the Pacific," Students' Observatory. Berkeley, Cal.. in order that arrangemeoli owy be made for transportation, lodging, etc. -^^H PUBLICATIONS ISSUED BI-MONTHLY. ^^H IFibmdry. April, June. AuguH. Octabir. Dtctmbir.'i ^^^ ( £ c X a «a a a> (/) W M :^S X c5i X ^Z^ s CI — - s:::) 01 »n — o CN PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XX. San Francisco, California, June 10, 1908. No. 120. METHODS OF DETERMINING THE ORBITS OF SPECTROSCOPIC BINARIES. By Heber D. Curtis. With the constantly increasing number of discoveries in this field of spectrograph ic research, the subject of spectroscopic binaries as a whole has become an exceedingly important one in its bearing on theories of stellar evolution. Thirty, or even twenty, years ago it would have seemed beyond the bounds of reasonable conjecture that at least one in every seven or eight of the brighter stars should prove to be a double star whose components are impossible of separation in any tele- scope existing or whose constniction is conceivable. It is unnecessary to speak of the importance of the results already secured in relation to theories of cosmogony. As one con- clusion only, we are led to think that our Sun, with its retinue of small planets, may possibly be a rather exceptional case in stellar development, the more common case being the fissiq^ of a star into two or more masses of the same order of magnitude. The number of these systems is increasing to-day at a rapid rate. Including those whose binary character is under inves- tigation, but not sufficiently substantiated for publication, the number is now about two hundred ; and, with the carrying of spectrographic surveys down to fainter stars, we may need four figures to express the total in the not distant future. It seems improbable at present that the labor of "keeping track" of all these systems will ever present the difficulties which make the asteroid group rather an embarrassing source of astronomical wealth, though we cannot, of course, premise 134 Publications of the just what interesting developments may be gained as to the inner mechanism of these systems from a comparison of their orbits of to-day with their forms one hundred years hence. It is not too much to suppose that the student of celestial mechanics may then find in this field "laboratory demonstra- tions" of the problem of three or more bodies, while possible changes in the periods and eccentricities could be expected to give valuable results to the worker in theories of tidal evolution of planets and satellites. In the sphere of double stars we now have an unbrokeij. continuum, from the spectroscopic binary of a few hours' rotation period to the visual double star with a period so long that centuries will be necessary for an accurate determination of the orbital elements. Some five or six stars are known to be both spectroscopically and telescopically double, and these serve to bind together the two fields. Visual double-star observers to-day are agreed that the greatest present progress in their branch of this wide field is to be derived from the systematic measurement of the systems of shorter period, from five to fifty years. It is in just this point of shortness of period that the spectroscopic field has the advantage in the point of evolutional developments. To take an extreme case : In the interesting cjua(Irui)le system of Castor the published spec- trographic observations of a,, the fainter component, extend over eleven years and cover no less than fourteen hundred complete revolutions, while for the visual system the telescopic measures extending over one hundred years cover so short an arc that the visual elements must remain uncertain for a long time to come. The actual dctennination of the elements of a spectroscopic binary is comparatively easy. From twenty to thirty plates; if well distributed over the period of revolution, are ample, in most cases, to secure satisfactory values of the elements of the system. The securing of these plates is the time-consuming factor in the problem, however, which perhaps explains why, for about seventy-five per cent of known spectroscopic binaries, we are still without accruate elements. While a skilful observer of visual double stars can make and reduce a com- plete single set of measures in fifteen to twenty minutes, including in this the time taken in passing from one star of Astronomical Society of the Pacific, 135 his programme to another, from half an hour to two or more hours is required for the exposure time alone of a single spectrographic plate. Developing, measuring, and reducing, unless hut few lines are available in the spectrum, will take several hours more. From a consideration of these points it may easily be seen that the determination of the orbits of three or four hundred spectroscopic binaries would require in the neighborhood of ten thousand plates, — easily twenty years' work for a single observatory, however favorably located as to climatic conditions. Doubtless for some years to come the individual observa- tories possessing powerful spectrographs for radial-velocity detenninations will endeavor to compute the elements of the binaries discovered by themselves. But it seems probable that the time must come when there will be systematic co-operation, to some extent at least, in order to secure greater rapidity in utilizing the data at present available and to be accumulated, and to prevent unnecessary duplication of work.* As no recent treatment of the various methods for the determination of the elements of a spectroscopic binary exists iit English, it is the purpose of this paper merely to collect in accessible form some of the more approved methods of solving the problem, with a few hints as to the processes involved, but without pretending to advance any new matter on the subject. The more important papers on the subject may be referred to as follows: — Rambaut, M. N., Vol. LI, pp. 316 ff. WiLsiNG, A. N., 134, 90, 1893. Russell, A ph. J., 15, 252, 1902. Lehmann-Filhes, a. iV., 136, 17, 1894. ScHWARzsciiiLD, A. N ., 152, 65, 1900. Hauschinger, "Bahnbestimmung der Himmelskorper," pp. 647 ff. ZuRiiELLEN, A. N., 173, 353, 1907. Zurhellex, a. N., 175, 245, 1907. * For several years the Lick Observatory has been keeping records of work in this field. — a task necessitated by the need for systematizing its own efforts, — and as a result it was found wise to collect the material available in a "First Catalogue of Spectroscopic Rinaries" (Campbell and Curtis, Lick Observatory Bulletin, No. 79, 1905). From time to time, as the need arises, successive catalogues will be issueil.— W. W. C. 136 Publications of the Of these methods, that of Rambaut is considerably longer and more involved than later methods and need not be con- sidered here. Wilsing's method, as originally published, was suitable only for orbits of small eccentricity, but Dr. Russell has extended it so as to make it applicable to larger eccentricities as well. The method of Wilsing and Russell is purely analytical, and in time consumed is considerably longer than the geometrical methods of Lehmann-Filhes, Schwarzschild, and Zurhellen. It consists in finding a Fourier's series for the velocity in terms of the elements. It should be very useful in special cases, particularly when the period is so nearly a year that one part of the velocity-curve is not represented by any observations. Another special appli- cation suggested by Russell is its use as a method of trig- onometrical analysis in disentangling the superposed elements of a triple or other multiple system. These longer methods will not be further treated here. The spectroscopic plates give us a series of irregularly dis- tributed radial velocities of the star, and the first problem is the determination of the approximate period, which rarely offers any difficulty. This should be done as early as possible in order to distribute the plates evenly over the revolution period and to fill up any gaps which may have been left by earlier plates. Different series of plates will differ so widely in their arrangement that the determination of each particular period is a separate problem. The observation times are most conveniently expressed in Julian days and decimals of a day. By choosing an epoch, preferably a maximum or minimum near the beginning of the series, a probable approximate value of the period is easily secured by the use of co-ordinate paper. When a number of maxima and minima are well defined, wide divergencies in other regions of the curve may generally be removed by trying a new period, some sub-multiple of the first period assumed. Then by subtracting multiples of the adopted period from the observation dates all the observations are reduced to a curve covering one revolution beginning at the assumed epoch, with the abscissae as times from the adopted date of maximum or minimum, and the observed velocities as the ordinates. After the preliminary curve is drawn, by noting the deviations from the curve at points near the mean of the Astronomical Society of the Pacific, 137 maximum and minimum velocities, where a change in the periodic time will have the greatest effect, advisable changes in the preliminary assumed period are readily found by divid- ing the deviations of such critical observations, expressed in time, by the number of revolutions elapsed. A second curve may then be drawn, whose periodic time will generally be very close to the true one. For all this preliminary work a calcu- lating machine is a great time-saver, though a simple table of multiples of the period will be almost as rapid. For stars whose periods are almost exact multiples of a day, and short, it may be necessary to wait some time before observations can be secured over all the velocity curve. The same may be true for orbits nearly a year in length, unless the analytical method of WiLSiNG and Russell be used in these cases. After the period Has been determined as carefully as possible the "most probable curve" is drawn, by estimation, through the observation points as plotted ; and it is well to prolong this cur\'e through a revolution and a half, in order to be able to use the ingenious methods of superposition devised by ScHVVARzscniLD and Zurhellen. The errors in drawing this curve have considerable effect on the accuracv of the determination of the elements. The most probable curve which even a practiced hand may draw is not likely to be a perfect representation of the elliptic motion which caused it, as it is natural to bend the curve slightly in or out at various points to satisfy the more or less exact observations. This difficulty is fundamental in all methods of treatment, and for it there seems to be no remedy other than by testing rapidly the first orbit found by a trial ephemerts and making the needful small changes in the elements, to which reference will be made later.^ * Though Zurhellen mentions this unavoidable curve-error earlier in his valu- able paper, it appears that he has not duly taken it into account, in the comparisons which he makes at the close of his paper, of the values of (i> and the eccentricity secured by his methods and those obtained by other investigators using other methods. His values, it is true, are quite close to the values secured, in some cases, by a rigorous least-square solution, but his values have evidently been derived from the final curves as published. These, of course, are accurately drawn from ephemerides and are very approximately true representations of the line of sight component of the velocity in an elliptic orbit. Had he applied his methods to the original preliminary curves used by the investigators with whose work he makes comparisons, he would doubtless have found values as far removed from the final ones as are the preliminary values secured by the method of Lehmann- 138 Publications of the Figure 2 gives a preliminary velocity-curve as actually drawn for the determination of the orbit of the spectroscopic binary #c Velorum, The observations used were as follows: — Julian Day, G. M. T. Vel. Julian Day, G. M. T. Vel. 2416546.739 + 68.5'"» 2417686.591 + 33-8""' 60.703 + 12.9 91.572 + 382 97651 + 65.7 92-545 + 43-2 6912.601 + 53-3 96.480 + 46.7 7587.844 + 58.6 7701.494 + 52.7 88.788 + 57-9 41.466 + 22.1 90.829 + 58.5 46.463 + 0.3 91.824 + 64.8 49.470 - 7-6 97.788 + 65.8 50.479 8.8 7609.790 + 62.0 51-463 13-3 54-534 — 21.0 53-457 — 19.2 55556 — 19.2 58-451 — 29.0 58.570 '5-2 59.460 — 24.6 59.545 — 14.5 The small circles representing the first four observations, which are important in deteniiining the period, owing to their distance in time from the later ones, are barred in the diagram. The period, (/, was assumed to be 116.65 days, and the begin- ning of the curve is at Julian day 2416476.0. This is not exactly at a minimum, as may be seen from the diagram. The conditions of the problem are illustrated in Figure i. The XY-plane is taken as the plane tangent to the celestial sphere at the center of motion, the Z-axis being the line of sight in which the velocities are measured, and perpendicular to the XY-plane. The orientatioiT of the X and Y axes in space remains unknown. It will be seen at once that the FiLiiis. Taking tlu' final curve of a.. Gcvitnorum as published, and using a planimettT, I find hy the method of LEiiM.xNN-KiLHts the following values: — Lchmann-Filhes. Final Elements. c 33 0.5111 t* :^^ 0.503 0, = -65°.36 ^^ — 265^35 UsinK the same procedure for tlie curve of fj Aitri^ir as published with Zurhellen's paper, I derive j^n^ 0.144, '» close agreement with the value from his method No. 8. (..'^=0.14^); for both his nuthod Xo. 8 and that of LEiiMANN-FiLHfes arc equally dt r \/p )]. These substitutions give for the fundamental equation (0 dc f -rr = — ^=^ sin i (cos u 4- e cos a>). dt y/, is determined with reference to the center of gravity of the system and the constant of attraction has the value km i where k is the Gaussian constant. If both components arc visible in the spec- trum and the motion of one mass with reference to the other is determined. Astronomical Society of the Pacific. 141 Now the curve of the observed velocities will have the gen- eral appearance of a distorted sine-curve with a maximum and a minimum at the points A and B in Fig. 2, but it is evident that the curve as a whole is shifted a distance above or below the zero -axis by an amount equal to the velocity of approach or recession of the binary system as a whole, and before the observed values can be made purely periodic the velocity of the center of mass of the system, which is a constant quan- tity for a single system, must be eliminated from the observa- tion values. Methods of finding the position of the line repre- senting the velocity of the center of mass of the system will be noted later, but for a study of some of the properties of the curve we will suppose for the present that this velocity of the system as a whole is known, and is represented by the dotted line in Fig. 2. This will be called the V-axis. It is evident from equation f i ) that for a maximum velocity cos M = I, and for a minimum cos 7/ = — i ; i. e., at the point A of the curve, w =: o ; and at B, u = 180° ; or, A and B are the points corresponding to the star's passage through the ascending and descending nodes of its orbit, respectively. Taking, then, A and B as the magnitudes of the curve ordi- nates at the points of maximum and minimum reckoned from the V-axis, B being taken as a positive quantity, we have A = ~; " sin 1(1+^ cos w) , y/P B = ~ , ■ sin t ( I — e cos w) . VP From these equations it is clear that the term ~7= sin i is the half amplitude of the curve in Fig. 2. This will be denoted by K, — i. e. / . . ^ A + B sin 1 = A = y/P 2 / . . A — B - sini = 94^.4. An entirely analogous equation may be used in case the posi- tion of the \'-axis is known. This is generally most accu- rately determined by a planimeter and the method of Leiimann-Filiies, to be given later, but may also be found from the mean axis by the requirement that the V-axis must 144 Publications of the lie at a distance equal to — K e cos , due in its simplified form to ZuRHFXLEN, is best when a> is small. It consists in finding the points on the velocity-curve where the true anomaly is equal to ±: 90°. From the fundamental equation, dc f, = -^ V = K (sin io -{- e cos w) , for z/ = — 90**, and f 2 = T' — J' = K ( — sin to) + ^ cos (I)) , for z/ = + 90® at or, ^^ = -\- K sin w. f 2 ^= — ^ sin a>. Moreover, at the points v= it 90°, /ij — /l2» M, = — M2, f, — 7 = — f/, — 7): hence these points lie symmetrically in f to the mean axis, and in time to the periastron. They may accordingly be deter- mined by rotatinjLT the curve copy 180° about the point of intersection of the ordinate of periastron with the mean axis, when the two intersections of the copy with the original curve will j^^ive the points sought. The point 7' = -|- 270° may be found in like manner. As a check on the location of these points draw the lines connecting the points v ^ -\- 270° and V =r: — 90*^, also that from z- = — 90° to z^ =r -f 90 <^. These lines should cut the mean axis at its intersections with the ordinates of apastron and periastron, respectively. Calling the ordinates measured from the mean axis fi for the point z; = — 90°, and C2 for the point 7' = -|- 90°, then sni o) = -ZJ ^_2 ., or tan w 2K ^^ — U This method is at its least advantage in the example given in Fig. 2, for here w is close to 90*^. At 7: = — 90° in the figure Astronomical Society of the Pacific. 145 we find its ordinate from the mean axis to be +46.1, while for z; = -|- 90° we find — 45.4. Hence sin w = 91 -5/ 93-2, and w = ioi°.o. Other interesting properties of the velocity-curve and meth- ods for finding the periastron-angle and eccentricity are de- rived by ZuRH ELLEN. For instance, by rotating the curve copy about the intersection of the periastron ordinate with the V-axis instead of with the mean axis, we may find the curve points where the eccentric anomalies are equal to ± 90^. But these additional methods will not in general offer any advantages over those already given. METHODS OF DETERMINING THE ECCENTRICITY. I. Perhaps the best is Zurhellen's method of drawing the tangents to the curve at the points of periastron and apastron. These can be drawn with considerable accuracy, except when the periastron falls near a maximum or minimum of the curve, for in this case slight changes in the position of periastron will cause considerable changes in the inclinations of the tangent-lines. The expression for the tangent will be f/f 27r jrf{ 2^ I dC dt ~~ U dM ~~ U I — ^ cos £ rf£ ' From u^v-\-iay and by introducing the known values cos E — sin . cos sin E cos V =: ?^ f Sm r =: - - I — e cos E I — e cos E the original velocity equation will take the form -. ds , . cos cos sin E . 4 ^ -77 = A cos <^. -, — -9 dt I — e cos E whence dt 2ir ., — COS COS 0) sin £ — sin w cos £ -I- ^ sin -77 ==-77 A cos <^. p =:T-r ' dt U ^ (i — ^cos£)' At periastron £ = o, and at apastron £ = tt ; whence df — 2jr'K cos sin sin (II 146 Publications of the From these values tan tan ■:=(t^)-=-'' or e ^ -\- In Fig. 2 the vakie of the tangent at periastron is I04°.8. while at apastron it is 60^.9 ; whence q = 1.45 and e = 0.18. 2. Draw the \^-axis and determine the ordinates from this axis of the maximum and the minimum, and also of peri- and apastron. Using ^ for these ordinates, f I c . "^max 1^ *'mln /» ^_^ «~ 3. The following method is that of Schwarzschild as sim- plified by ZuRHELLEN. It is best when a> is small, and to be applicable for eccentricities over 0.2 implies the use of Schw.xkzscuild's table, of which the necessary portion is given below. It depends upon the difference in time of the ordinates of the points v =^ z^z 90°, before determined. Since tan 3/2 /i = tan >4 7' tan (45° — J/2 <^), for z^= zp 90°, we have tan V2 7' = i;i i, and therefore i^i = — (90° — <^) and Zi. = + ([)0'^ — y Similarly, M, _ _ (90 -) + ^^v . Af„ =. + ( c^o _ ^ ) _ J^i^ can then be taken directly from Schwarzschild's table. For small values of c ( < \2-\ e < 0.2) the table may be replaced by the shorter formula, From Fig. 2 we have f, =80.0 days, t. = 117.8 days, hence -^r — - — 0..S24 ; whence from the table, 90^ — <^ nz 73^.7 and e = 0.28. Using the shorter formula, r = 0.27. The di- Astronomical Society of the Pacific. 147 vergence from the other values which have been secured is because w is so near to 90°, the most unfavorable case for this method. schwarzsciiild's table for the equation t., — /, 2 w — SIN 2 w = 2 TT — , u '2 — ', V ^ — ', V f, — f, V u u u 0° 0.0000 30° 0.0290 60° 0.1956 I 0.0000 31 0.0318 61 0.2040 2 0.0000 32 0.0348 62 0.2125 3 0.0000 33 0.0380 63 0.2213 4 0.000 1 34 0.0414 64 0.2303 5 0.000 1 35 0.0450 65 0.2393 6 0.0002 36 0.0488 66 0.2485 7 0.0004 37 0.0527 67 0.2578 8 0.0006 3« 0.0568 68 0.2673 9 0.0008 39 0.061 1 69 0.2769 10 0.00 IT 40 0.0656 70 0.2867 II 0.0015 41 0.0703 71 0.2966 12 0.0020 42 0.0751 72 0.3065 13 0.0025 43 0.0802 73 0.3166 14 0.0031 44 0.0855 74 0.3268 IS 0.0038 45 0.0910 75 0.3371 16 0.0046 46 0.0967 76 0.3475 17 0.0055 47 0.1025 77 0.3581 18 0.0065 48 0.1085 78 0.3687 19 0.0077 • 49 0.1 147 79 0.3793 20 o.oo8() 50 0.1212 80 0.3900 21 0.0103 51 0. 1 278 81 0.4008 22 0.0117 52 0.1346 82 0.41 17 23 0.0133 53 0.1416 83 0.4226 24 0.015 1 54 0.1488 84 0.4335 25 0.0170 55 0.1 561 85 0.4446 26 0.0191 56 0.1636 86 0.4557 27 0.02 1 3 57 0.1713 87 0.4667 28 0.0237 58 0.1792 88 0.4778 29 0.0262 59 0.1873 89 0.4889 30 0.0290 60 0.1956 90 0.5000 148 Publications of the METHOD OF LEHMANN-FILHES. It has not seemed advisable to segregate the separate steps in this method for inckision with the other methods given before. The method of Lehmann-Filhes will be found very generally useful, and little, if any, longer than other methods, providing a planimeter is used. Given the observations and the velocity-curve, the first step is the fixing of the position of the velocity of the center of gravity of the system, — the so-called V-axis. This is found by the requirement that the integral of ds/dt, — ^that is, the area of the velocity-curve, — must be equal for the portions of the curve above the \'-axis and below it. By far the easiest method of performing this integration is to use a planimeter. A line is first drawn by estimation as nearly in the correct position to fulfil the requirement of equal areas as can be judged by the eye. Placing the planimeter pointer at the intersection of this line and the curve, trace out the curve lying on one side of the line in, say, a clockwise direction, and, on reaching the starting point, traverse the portion of the curve on the other side of the line, in the counter-clockwise direction. The readings of the planimeter will then give directly the difference in the two areas, and the position of the V-axis may be shifted slightly to correct the difference. A second double circuit by the planimeter will generally be all that is necessary to secure an accurate value of the position of the V-axis, not depending simply upon the magnitude of maximum and minimum as in the previous methods, but sup- ported by the entire curve. The increased accuracy is of little importance, however, as it will be found best to correct what- ever value of V may be adopted by the residuals from the final ephemeris. If a planimeter is not available, doubtless the best method to equalize the areas above and below the curve will be to draw the curve on cross-section paper and make a count of the small squares, as suggested by Rambaut. The position may also be found by an approximate mechanical integration, as advised by Lehmaxn-Filties, but in such a case the shorter methods explained above for finding the elements would generally be given the preference. Given the position of the V-axis, the ordinates should next be drawn at the points of maximum and minimum velocity Astronomical Society of the Pacific. * 149 (Aa, Bb in Fig. 2). It is at this point that this method is weakest and most subject to error, for slight errors in the fixing of the positions of these ordinates may easily arise. It is best to check the positions of these ordinates by the require- ment that the curve portion AaC must be equal in area to Q>B, while DaA = BbD. Considering V as eliminated from the velocities, at the curve points C and D, we have ds/dt = o ; hence, from the fundamental velocity equation, A — B cos u ^ — e cos w = — A + B The argument of the latitude, Wi, corresponding to the point C, lies on the way from the ascending to the descending node, hence sine u^ is positive. Then, sin M, := 2VAB A + B r • cos M, — A B A + B ^ ' — e cos a> ; while for Mj at the point D sin U2 = — 2VAB A + B — sin Ml, cos Mj — A B A 1 -D — COSM,. Denoting the area of AaC by Z^, and bBD by Zj (it will be seen that these areas represent the distances of the star from the XY-plane when at the points of its orbit cor- responding to the arguments of the latitude u^ and Wj) and the radii vectors by r^ and rj, we have Z, = r, sin 1 sin u^, Z2 = ^2 sin i sin u^ = — r^ sin i sin u^, ^2 ^2 150 Publications of the Then, since r, = * I + ^COS (Ui ft)) P w= * I + ^ cos (Uj + ft>) I + ^ COS Wi COS ft) — ^ sin u^ sin «) Z, . I + ^ cos Wj cos ft) + ^ sin tij sin ft) Z, and, since cos u^:= — e cos ft), Whence, sin tti — ^ sin ft) Z, sin «! + ^ sin ft) Z, ^ sm ft) = -=^= =- sin u,, ^2 ^1 which may be written in the form ^dn _^V^ Z2 + Z, ^'^""- atb-zt^z:- As it was found earlier from a consideration of the values A and B that A — B e cos iii '=■ A + B these two equations give all that is needed for a determination of e and w. The values of A and B are taken from the curve, and the areas Z, and Z.^ are quickly integrated from the curve portions AaC and bBD by means of a planimeter (the latter area is considered negative in sign and the unit of area used is entirely immaterial as only the ratios of the areas are required). At the time of passing through periastron « = &>, whence from the fundamental equation dz =1 K (i -{- e) cos w. d/p Knowing K, e, and oj, detennine this value, and the abscissa of the point on the curve which has the above value as ordinate will give the value of T when properly combined with the Astronomical Society of the Pacific. 151 epoch used for the beginning of the curve. As at the points A, B, and A,, u equals o, tt, and 27r, respectively, and as w is known, there will be no ambiguity as to the position of w = w. We may instead determine the eccentric anomaly at the point C where «i is known, and then find the time from peri- astron, /i, corresponding to this value of u^ by the well-known formulae tan £, 2 Vt — e tan"- — :;: 2 Hh 2 1908. Gr. M. T. 4. ^. June 15. Disapp. I7h 40m 7".! 232 15. Reapp. 20 7 I .9 189 20. Disapp. 6 9 7 -2 232 20. Reapp. 8 32 2 .1 191 24. Disapp. 18 38 7 4 231 24- Reapp. 20 57 2 .3 192 29. Disapp. 7 7 7 .5 231 29. Reapp. 9 22 2 .5 193 July 3. Disapp. 19 36 7 .5 230 3. Reapp. 21 47 2 .6 193 8. Disapp. 8 5 7 .5 230 8. Reapp. 10 13 2 .7 194 12. Disapp. 20 34 7 4 229 ' 12. Reapp. 22 38 2 .8 194 17. Disapp. 9 4 7 .3 228 17. Reapp. II 2 2 .8 195 21. Disapp. 21 33 7 .1 228 21. Reapp. 23 27 2 .8 195 26. Disapp. 10 3 6 .8 227 26. Reapp. II 52 2 .8 195 30. Disapp. 22 32 6.5 226 31. Reapp. 0 16 2 .7 195 Aug. 4. Disapp. II 3 6 .2 225 4. Reapp. 12 40 2 .7 195 8. Disapp. 23 33 5 .8 224 9. Reapp. I 5 2 .6 195 13. Disapp. 12 3 5 -3 222 13. Reapp. 13 28 2 .5 194 18. Disapp. 0 34 4 .8 220 18. Reapp. I 52 2 .3 194 22. Disapp. 13 6 4 .3 218 22. Reapp. 14 15 2 .1 193 27. Disapp. I 38 3 .6 215 27. Reapp. 2 38 I -9 193 31. Disapp. 14 II 3 0 211 31. Reapp. 14 59 I .8 193 Sept. 5. Disapp. 2 46 2 .4 207 5- Reapp. 3 19 I .6 193 9. Eclipse? 15 29 I .5 198 ( Heliocentric conj.) 14. Eclipse? 3 57 • • • • • • (Heliocentric conj.) 18. Eclipse? 16 ^4 . « • • • • • (Heliocentric conj.) 7 8 16 pn Qm 8 42 [8 27 8 8 7 53 7 34 7 18 6 59 6 43 6 24 6 8 5 48 5 32 5 II 4 SI 4 35 4 14 3 57 3 37 3 20 2 59 2 42 In computing these data, the values of the semi-axes of the planet were assumed to be : a = 8''.735, b = 7".825, at the mean distance. On this supposition the latest eclipse of Rhea will take place September 5th. Supposing the semi-axes o".i larger, the end of the cycle of eclipses falls on the date Sep- Astronomical Society of the Pacific. 159 tember 9th, and the times of disappearance and reappearance will change by the quantities, expressed in minutes, given in the column headed "dt for da = o".i." The predicted times might therefore be changed greatly by the size of the planet, by the penumbra, etc., which could here not be taken into account. It will be worth while to watch the satellite until its latest eclipses, in September, and to ascertain precisely the end of their cycle. For these observations, also, photometers may be used with success, as the brightness of the satellite will vary slowly. Eclipses of the Inner Satellites of Saturn, 1908. Disappearance before opposition. s and p denote the geocentric place of the satellite at the time of its disappear- ance— i. e. the distance from the limb of the planet, and the position-angle, counted from the north point of the minor axis to the east. 1908. Gr. M. T. s. p. 1908. Gr. M. T. s. ^ uly I. Mi. 23! 1 4m 2" \6 256^ July 10 . Di. 4h i6m 5" '7 239* • Di. 23 10 5 .7 239 Mi. 10 38 2 .6 256 2. Te. II 34 4 .5 243 En. 19 20 3 .6 248 En. 14 0 3 .6 248 II. Mi. 9 16 2 .6 256 Mi. 21 41 2 .6 256 Te. 22 8 4 .5 243 3. Rh. 19 36D 7 .5 230 12. En. 4 13 3 .6 248 Mi. 20 18 2 .6 256 Mi. 7 53 2 .6 256 Rh. 21 47 R 2 .6 193 Rh. 20 34D 7 .4 229 En. 22 54 3 .6 248 Di. 21 58 5 .7 238 4. Te. 8 52 4 .5 243 Rh. 22 38R 2 .8 194 Di. 16 52 5 .7 239 13. Mi. 5 30 2 .6 256 Mi. 18 56 2 .6 256 En. 13 6 3 .6 248 5- En. 7 47 3 .6 248 Te. 19 27 4 .5 242 Mi. 17 33 2 .6 256 14. Mi. 4 7 2 .6 256 6. Te. 6 II 4 .5 243 En. 21 59 3 .6 248 Mi. 16 10 2 .6 256 15. Mi. 2 44 2 .6 256 En. 16 40 3 .6 248 Di. 15 40 5 .6 238 7. Di. 10 34 5 .7 239 Te. 16 46 4 .5 242 Mi. 14 47 2 .6 256 16. Mi. I 21 2 .6 255 8. En. I 33 3 .6 2/l8 En. 6 52 3 .6 248 Te. 3 30 4 .5 243 17. Mi. 0 59 2 .6 255 Rh. 8 5D 7 .5 230 Rh. 9 4D 7 .3 228 Rh. 10 13 R 2 .7 194 Rh. II 2R 2 .8 195 Mi. 13 24 2 .6 256 Te. 14 4 4 .5 242 9. En. 10 26 3 .6 248 En. 15 46 3 .6 2/l8 Mi. 12 I 2 .6 256 Mi. 23 36 2 .6 255 10. Te. 0 49 4 •5 243 18. Di. 9 22 5 .6 238 i6o Publications of the 1908. Gr. M.T. * r. P- 1908. Gr. M.T. s. #. July 18. Mi. 22^ 13" 2" .6 255^ Aug. 3. En. 2* 124™ S^'S 247' 19. En. 0 39 3 .6 248 Te. 13 54 4 .0 241 Te. II 23 4 •4 242 Di. 19 35 5 .0 236 Mi. 20 50 2 .6 255 Mi. 22 46 2 A 254 20. En. 9 32 3 .6 2/l8 4. Rh. II 3D 6 J2 225 Mi. 19 27 2 .6 255 En. II 17 3 2 247 21. Di. 3 4 5 .5 238 Rh. 12 40R 2 7 195 Te. 8 42 4 .4 242 Mi. 21 23 2 A 254 Mi. 18 5 2 .6 255 5. Te. II 13 4 .0 241 En. 18 25 3 .6 248 Mi. 20 0 2 A 254 Rh. 21 33 D 7 .1 228 En. 20 II 3 -2 247 Rh. 23 27 R 2 .8 195 6. Di. 13 18 4.8 236 22. Mi. 16 42 2 .6 255 Mi. 18 37 2 .3 254 23. En. 3 18 3 .5 248 7. En. 5 4 3 .2 247 Te. 6 I 4 .4 242 Te. 8 32 3 .9 241 Mi. 15 19 2 .6 255 Mi. 17 14 2 .3 254 Di. 20 46 5 .5 238 8. En. 13 57 3 .1 247 24. En. 12 12 3 .5 248 Mi. IS 52 2 .3 254 Mi. 13 56 2 .6 255 Rh. 23 33 D 5.8 224 ^5. Te. 3 20 4 .3 242 9. Rh. I 5R 2 .6 195 Mi. 12 33 2 .6 255 Te. 5 50 3.8 240 En. 21 5 3 .5 248 Di. 7 0 4.6 236 26. Rh. 10 3D 6 .8 227 Mi. 14 29 2 .3 254 Mi. II II 2 •5 255 En. 22 50 3 I 247 Rh. II 52 R 2 .8 195 10. Mi. 13 6 2 .2 254 Di. 14 29 5 •4 237 II. Te. 3 9 3 -7 240 27. Tc. 0 38 4 •3 241 En. 7 44 3 .0 247 En. 5 5« 3 248 Mi. II 43 2 .2 253 Mi. 9 48 2 .5 255 12. Di. 0 42 4 .4 236 28. Mi. 8 25 2 .5 255 Mi. 10 21 2 .2 253 En. 14 51 3 •4 248 En. 16 37 ' 3 .0 247 Te. 21 57 4 .2 241 13. Te. 0 28 3 .6 240 29. Mi. 7 2 2 .5 254 Mi. 8 58 2 .2 253 Di. 8 II 5 •3 237 Rh. 12 3D 5 .3 222 En. 23 44 3 •4 248 Rh. 13 28 R 2 .5 194 30. Mi. 5 39 2 .5 254 14. En. I 30 2 .9 247 Te. 19 16 4 .2 241 Mi. 7 35 2 .1 253 Rh. 22 32 D 6 .5 226 Di. 18 24 4 .2 235 31. Rh. 0 16 R 2 .7 195 Te. 21 47 3 .5 240 Mi. 4 17 2 .5 254 15. Mi. 6 12 2 .1 253 En. 8 38 3 •3 247 Kn. 10 23 2 .9 247 Aug. I. Di. I s^ 5 .2 237 16. Mi. 4 50 2 .1 253 Mi. 2 54 2 254 Te. 19 6 3 .4 240 Te. 16 3S 4 .1 241 En. 19 16 2 .8 247 En. 17 31 3 •3 247 17. Mi. 3 27 2 .1 253 2. Mi. I 31 2 .5 254 Di. 12 7 4 .0 235 3- Mi. 0 8 2 •4 254 18. Rh. 0 34D 4.8 220 Astronomical Society of the Pacific. i6i 1908. Aug. 18. Rh. Mi. En. Te. 19. Mi. En. Mi. 20. Di. Te. Mi. En. 21. Mi. 22. En. Te. Rh. Rh. Mi. Di. 23. En. Mi. 24. Te. Mi. 25. En. Mi. Di. 26. Te. En. Mi. 27. Rh. Rh. Mi. En. 28. Te. Mi. Di. 29. En. Mi. 30. Te. Mi. En. 31- Di. Mi. Rh. Rh. En. Te. Sept. r. Mi. Gr. M. T. I»»52«>R s. 2 .3 2 4 2 .1 4 10 2 .7 16 25 3 .3 0 41 2 .0 13 3 2 .7 23 19 2 .0 5 49 3.8 13 44 3 .2 21 .56 2 .0 21 56 2 .6 20 33 I .9 6 49 2 .5 " 3 3 0 13 6D 4 .3 14 15 R 2 .1 19 10 I .9 23 31 3.6 15 43 2 .5 17 48 I .8 8 22 2 .9 16 25 I .8 0 36 2 .4 15 2 . I 7 17 14 3 .4 5 41 2 .8 9 29 2 4 13 40 I .7 I 38D 3.6 2 38R I .9 12 17 I 7 18 22 2 .3 3 0 2 7 10 54 I 7 10 56 3 .2 3 16 2 .2 9 32 I .6 0 19 2 .5 8 9 I .6 12 9 2 .1 4 38 3 .0 6 46 I .5 14 II D 3 .0 14 59 R I .8 21 2 2 .0 21 38 2 .4 5 23 I .5 ^ 194' 253 247 240 253 247 253 234 239 253 247 253 247 239 218 193 253 234 247 252 239 252 247 252 234 239 246 252 215 193 252 246 238 252 233 246 252 238 252 246 233 252 211 193 246 238 252 1908. Sept. 2. 3. 4. Gr. M. T. Mi. 4^ I°» En. 5 56 Te. 18 57 Di. 22 21 Mi. 2 38 En. 14 49 Mi. I 15 Te. 16 16 En. 23 42 s. ^ 5. 6. Mi. Rh. Rh. Di. Mi. En. Te. Mi. 23 53 2 46D 3 19R 16 3 22 30 8 36 13 35 21 7 7. En. 17 29 8. 9. 10. II. 12. 13. 14. IS. 16. Mi. Di. Te. Mi. En. Rh. Mi. Te. En. Mi. Di. Mi. En. Te. Mi. -En. Mi. Di. Te. Rh. Mi. En. Mi. 19 44 9 46 10 54 18 22 2 22 15 29 16 59 8 13 11 16 15 36 3 28 14 14 20 9 5 32 12 51 5 2 II 28 21 II 2 51 3 57 10 6 13 56 8 43 En. 22 49 Te. o 10 17. Mi. Di. Mi. En. 7 20 14 53 5 58 7 42 I "-5 252** 1 .9 246 2 .2 238 2 .8 232 I u^ 252 I .8 246 1 .4 251 2 .1 237 I .8 246 1 A 251 2 .4 206 1 .6 193 2 .5 231 I .3 I 7 251 246 I .9 237 I .3 251 I .6 246 1 .2 251 2 .2 231 I .8 237 I .2 251 I .6 246 Eclipse ? I .1 251 I .6 236 I .5 246 I .1 251 I .9 230 I .0 251 I .4 246 I .5 236 I .0 251 I .3 246 0 .9 250 1 .6 229 I .4 236 Eclipse ? 0 .9 250 1 .2 246 0 .8 250 1 .1 246 I .2 235 0 .8 250 1 .3 228 o .7 250 1 62 Publications of the 1908. Gr. M.T. < r. ^ 1908. Gr. ; M.T. 4 f. P- Sept. 17 .Te. 21* '29™ i" .0 235** Sept. 2^ i. En. 4» I gm 0" '.5 245' 18. Mi. 4 35 0 .7 250 Mi. 18 56 0 .3 249 Rh. 16 24 Eclipse? Di. 20 I 0 A 226 En. 16 36 0 .9 245 25. Te. 10 45 0 A 234 19. Mi. 3 12 0 .6 250 En. 13 2 0 A 245 Di. 8 36 I .0 228 Mi. 17 34 0 .3 249 Te. 18 48 0 .9 235 26. Mi. 16 II 0 ^ 249 20. En. I 29 0 .8 245 En. 21 56 0 .3 245 Mi. I 50 0 .6 250 27. Te. 8 4 0 .2 233 21. Mi. 0 27 0 .5 250 Di. 13 44 0 .1 225 En. 10 22 0 .7 245 Mi. 14 48 0 J2 249 Te. 16 7 0 .7 234 28. En. 6 49 0 ^ 245 Mi. 23 4 0 .5 249 Mi. 13 26 0 .1 249 22. Di. 2 18 0 .7 227 29. Te. 5 23 0 .1 233 En. 19 16 0 .6 245 Mi. 12 3 0 .1 249 Mi. 21 42 0 .4 249 En. IS 42 0 .1 245 23. Te. Mi. 13 20 26 19 0 0 .6 .4 234 249 30. Mi. 10 41 0 .0 248 Reappearance after opposition. s and p denote the geocentric place of the satellite at the time of its reappear- ance— i. e. the distance from the limb of the planet, and the position-angle, counted from the north point of the minor axis to the east. 1908. Gr. M.T. < f. P- 1908. Gr. M.T. f. P- Oct. I. En. 2h57ni 0" r .0 115^ Oct. 10. Mi. 21* '37^^ 0" •3 iij Mi. II 24 0 .0 113 II. Di. 8 18 0 .0 132 2. Mi. 10 2 0 .0 113 Mi. 20 14 0 •3 112 En. II 50 0 .0 115 12. En. 2 3 0 A 112 3- Mi. 8 39 0 .0 113 Te. 12 45 0 .2 125 En. 20 44 0 .1 115 Mi. 18 51 0 .3 III 4. Mi. 7 16 0 .0 113 13. En. 10 57 0 .5 112 Te. 23 30 0 .0 128 Mi. 17 29 0 •4 III 5. En. 5 37 0 .1 114 14. Di. 2 0 0 .1 130 Mi. 5 53 0 .1 113 Te. 10 3 0 .3 124 6. Mi. 4 31 0 .1 112 Mi. 16 6 0 .4 III En. 14 30 0 .2 114 En. 19 50 0 .5 112 Te. 20 49 0 .0 127 15- Mi. 14 43 0 A III Mi. 3 8 0 .1 112 16. En. 4 43 0 •5 III En. 23 24 0 .3 "3 Te. 7 22 0 •3 123 8. Mi. r 45 0 .2 112 Mi. 13 20 0 .4 III Di. 14 37 0 .0 133 Di. 19 41 0 .2 129 Te. 18 7 0 .1 127 17. Mi. II 58 0 •5 no 0. Mi. 0 22 0 2 112 En. 13 37 0 .6 III En. 8 17 0 •3 "3 18. Te. 4 41 0 .4 123 Mi. 23 0 0 2 112 Mi. 10 35 0 .5 no 10. Tc. 15 26 0 .1 126 En. 22 30 0 .6 III En. 17 10 0 .4 113 19- Mi. 9 12 0 .5 no Astronomical Society of the Pacific. 163 1908. Gr. ] M.T. s. ^ 1908. Gr. M. T. 1. ^ Oct. 19. Di. 13** 23™ 0 .3 1 [28** Nov. 6. Te. Ih48ni c ^^9 1 [18** 20. Te. I 59 0 .4 ] [22 Mi. 7 I 1 [ .0 ] [08 En. 7 23 0 .7 ] [10 7. En. 2 57 1 [ .3 ^ [07 Mi. 7 50 0 .5 ] [10 Mi. 5 38 1 [ .0 ] [08 21. Mi. 6 27 0 .6 ] [10 Di. 17 14 0 .9 ] [21 En. 16 17 0 .7 ] [10 Te. 23 6 0 .9 ] [I8 Te. 23 18 0 .5 ^ [22 8. Mi. 4 16 ] [ .0 ] [07 22. Mi. 5 4 0 .6 ] [10 En. II 50 1 \ .3 ] [07 Di. 7 4 0 .3 ] [27 9. Mi. 2 53 1 t .1 ] 107' 23. En. I 10 0 .7 1 no Te. 20 25 ] [ .0 ] [18 Mi. 3 42 0 .6 : [10 En. 20 44 1 [ .4 ) [07 Te. 20 37 0 .5 ^ [21 10. Mi. I 30 1 t .1 : [07 24. Mi. 2 19 0 .7 ] [09 Di. 10 55 c ) .9 ) [20 En. 10 3 0 .8 ] [09 II. Mi. 0 8 ] t .1 ] [07 25. Di. 0 46 0 A 1 [26 En. 5 37 1 : 4 ^ [07 Mi. 0 56 0 .7 ) [09 Te. 17 44 1 [ .0 ] [17 Te. 17 56 0 .6 ] [21 Mi. 22 45 1 t .2 ] [07 En. 18 57 0 .8 t09 12. En. 14 30 1 f .5 ^ [07 Mi. 23 33 0 .7 : t09 Mi. 21 22 ] [ .2 ] [07 26. Mi. 22 II 0 .7 ^ [09 13. Di. 4 %1 1 I .0 : [19 27. En. 3 50 0 .9 : [09 Te. 15 3 ^ [ .1 1 [17 Te. 15 14 0 .6 ] r20 Mi. 20 0 ] [ .2 ] [07 Di. 18 27 0 .5 : [24 En. 23 24 ] t .5 1 [07 Mi. 20 48 0 .8 ] [09 14. Mi. 18 37 1 [ .2 1 [07 28. En. 12 43 0 .9 [09 15. En. 8 17 1 f .5 1 [06 Mi. 19 25 0 .8 ] [09 Te. 12 22 1 [ .1 [17 29. Te. 12 33 0 .7 1 [20 Mi. 17 14 ] r .3 ^ [07 Mi. 18 3 0 .8 [09 Di. 22 18 ] [ .1 ] [19 En. 21 37 I .0 ] [09 16. Mi. 15 52 1 f .3 ] [06 30. Di. 12 9 0 .6 ] 123 En. 17 II ] t .6 ] [06 Mi. 16 40 0 .8 [09 17. Te. 9 40 1 [ .2 [17 31. En. 6 30 I .0 ] [08 Mi. 14 29 1 r .3 [06 Te. 9 52 0 .7 [19 18. En. 2 4 1 [ .6 ] [06 Mi. 15 17 0 .8 [08 Mi. 13 6 ] c .3 3 [06 Nov. I. Mi. 13 54 0 .9 [08 Di. 16 0 1 [ .1 118 En. 15 24 I .1 [08 19. Te. 6 59 1 [ .2 1 [16 2. Di. 5 51 0 .7 ] [22 En. 10 57 3 [ .6 ] [06 Te. 7 10 0 .8 [I9 Ml. II 44 1 [ 4 ^ [06 Mi. 12 32 0 .9 : [O8 20. Mi. 10 21 ] [ 4 [06 3. En. 0 17 I .1 1 [O8 En. 19 51 1 [ .7 ] [06 Mi. II 9 0 .9 [O8 21. Te. 4 18 ] t .3 : [16 4. Te. 4 29 0 .8 [I9 Mi. 8 58 ] [ .4 ] [06 En. 9 10 I .2 1 [O8 Di. 9 41 1 [ .2 ; [18 Mi. 9 46 0 .9 ] [O8 22. En. 4 44 ^ f .7 [06 Di. 23 32 0 .8 ] [22 Mi. 7 35 1 t .4 " [06 5. Mi. 8 24 I .0 [O8 23. Te. I Zl 1 r .3 [16 En. 18 4 I .2 [O8 Mi. 6 13 ] [ 4 ] [06 164 Publications of the 1908. No. 23. En. 24. Di. Mi. En. Te. 25. Mi. 26. Mi. En. Te. Di. 27. Mi. En. Mi. 28. Te. Mi. 29. En. Di. Mi. 30. En. Te. Mi. Dec. I. Mi. En. 2. Di. Te. Mi. 3. En. Mi. 4. Te. En. Mi. 5. Di. Mi. En. 6. Te. Mi. 7. En. Mi. Di. 8. Te. Mi. En. 9. Mi. 10. En. Te. Mi. Di. Gr. M. T. s. ^ 1908. Gr. Iff.T. s. ^. 13^3^ ] r.7 : [06** Dec. II . Mi. ^h 2™ I' \6 ] [04* 3 23 : [ .2 ] [18 En. 9 12 2 .0 105 4 50 ] I .5 ] [06 Te. 22 45 .5 "5 22 31 ] [ .8 ] [06 12. Mi. 2 39 .6 [04 22 56 ] [ .4 ] [16 En. 18 5 .0 ro5 3 27 ^ I .5 ] 105 13. Mi. I 16 .6 : [04 2 5 ] I .5 ^ 105 Di. 7 12 .2 [18 7 24 ] [ .8 ] [06 Te. 20 3 ■5 "5 20 14 ] t .2 ] [18 Mi. 23 54 .6 ] [04 21 4 ] [ 4 ] [16 14. En. 2 59 2 .0 105 0 42 ] t .5 ] 105 Mi. 22 31 .6 - [04 16 18 ] t .9 ] [06 15. En. II 52 .0 ; 105 23 19 1 t .5 ^ 105 Te. 17 22 .5 2 [16 17 33 1 t .4 : 115 Mi. 21 8 .6 : [04 21 57 ^ I .5 ] 105 16. Di. 0 54 .2 ] [19 I II ] [ .9 : 105 Mi. 19 46 .6 ] ro4 14 46 ] [ .2 ] [18 En. 20 46 2 .0 1 [06 20 34 1 t .5 1 ro5 17. Te. 14 41 .5 3 ti6 10 5 ^ [ .9 ] C05 Mi. 18 23 .6 ] [04 14 52 : t .4 ] 115 18. En. 5 39 2 .0 ] [06 19 II ] t .5 J 105 Mi. 17 0 .6 1 [04 17 49 1 [ .6 ] f05 Di. 18 35 .1 ] [19 18 58 ] c .9 ] fos 19. Te. 12 0 .4 1 [16 8 27 1 t .2 ] [18 En. 14 32 2 .0 ] [06 12 II 1 .4 ^ ri5 Mi. 15 38 .6 ] [04 16 26 1 [ .6 ] f05 20. Mi. 14 15 .6 ] [04 3 51 3 [ .9 ] f05 En. 23 26 2 .0 ] [06 15 3 1 [ .6 ] ro5 21. Te. 9 18 .4 ] [16 9 30 ] [ .4 ] [15 Di. 12 16 .1 ] 120 12 45 3 [ .9 1 ^05 Mi. 12 52 .6 ] [04 13 41 1 [ .6 ] 105 22. En. 8 19 2 .0 1 106 2 8 ] r .2 ] [18 Mi. II 30 .6 ] [04 12 18 ] r .6 ] f05 23. Te. 6 37 .4 ^ [16 21 38 ] [ .9 ] 105 Mi. 10 7 .6 ] [04 6 48 ] [ .4 1 115 En. 17 13 2 .0 ] [06 10 55 1 [ .6 ] f05 24. Di. 5 58 .0 1 [20 6 32 : J .0 ] to5 Mi. 8 44 .6 ] [O4 9 33 1 [ .6 ] f05 25. En. 2 6 2 .0 ] to6 19 50 ] [ .2 ] [18 Te. 3 56 .4 ^ H7 4 7 ^ [ .4 ] 115 Mi. 7 22 .6 ] [04 8 10 ] t .6 ] [04 26. Mi. 5 59 .7 1 [04 15 25 i J .0 1 to5 En. II 0 2 .0 1 106 6 47 ] [ .6 ] t04 Di. 23 39 .0 ] [21 0 18 : > .0 ] 105 27. Te. I 15 •4 3 117 I 26 ] [ .5 ] 115 Mi. 4 36 .7 ] ro^ 5 24 ] [ .6 ] [04 En. 19 53 2 .0 ] [06 13 31 1 r .2 ] ri8 28. Mi. 3 13 I .7 : [04 Astronomical Society of the Pacific. 165 1908. Gr. M. T. Dec. 28. Te. 22*>34™ 29. Mi. I 51 En. 4 47 Di. 17 20 30. Mi. 0 28 En. 13 40 Te. 19 52 Mi. 23 5 31. Mi. 21 43 En. 22 34 1909. Jan. I. Di. II I Te. 17 II , Mi. 20 20 2. En. 7 27 Mi. 18 57 3. Te. 14 30 En. 16 20 Mi. 17 34 4. Di. 4 42 Mi. 16 12 5. En. I 14 Te. II 48 Mi. 14 49 6. En. 10 7 Mi. 13 26 Di. 22 22 7. Tc. 9 7 Mi. 12 4 En. 19 I 8. Mi. 10 41 9. En. 3 54 Te. 6 26 Mi. 9 18 Di. 16 3 10. Mi. 7 55 En. 12 47 II. Te. 3 45 Mi. 6 ZZ En. 21 41 12. Mi. 5 10 Di. 9 44 s. ^ l"A ^ 117^ I .7 [04 2 .0 ] [06 0 .9 : [21 I .7 [O4 2 .0 . [06 I .4 117 I .7 ^ [O4 I .7 : [O4 I .9 [O6 0 .8 ] [22 I .3 [I8 I .7 \ [O4 I .9 ^ [O6 I .7 ] [O4 I .3 [18 I .9 ] [O7 I .7 : [O4 0 .7 ] 123 I .7 ] [O4 I .9 ] to7 I .3 ^ ti9 I .7 ] [04 I .8 : t07 I .7 ] [04 0 .6 ] [24 I .3 ] [I9 I .7 ) [04 I .8 ] [07 I .7 \ [04 I .8 ] [07 I .2 ] [19 I .6 ] [04 0 .5 ] 125 I .6 ] [04 I .8 ] [07 I .2 ] [20 I .6 ] [O4 I .8 : [08 I .6 ] [O4 0 .4 1 [26 1909. Jan. 13. Te. Mi. En. 14. Mi. En. Te. 15. Mi. Di. Mi. 16. En. Te. Mi. 17. En. Mi. Di. 18. Te. En. Mi. 19. Mi. 20. En. Te. Di. Mi. 21. En. Mi. 22. Te. Mi. En. 23. Di. Mi. 24. En. Te. Mi. 25. Mi. En. 26. Te. Mi. En. 2^. Mi. 28. Te. Mi. En. Gr. M. T. 3 47 6 34 2 24 15 28 22 22 I 2 3 24 23 39 o 21 19 41 22 16 9 14 20 53 21 4 17 o 18 8 19 31 18 8 3 I 14 18 14 44 16 45 II 55 15 ^ 11 Z1 14 o 20 48 8 24 12 37 5 42 8 56 II 14 9 51 14 35 6 15 828 23 28 7 6 3 ZZ 5 43 8 22 s. ".2 .6 .8 .6 .8 .1 .6 0.3 .6 .8 .1 .6 .7 .5 o .2 .0 .7 .5 •5 .7 .0 0 .1 .5 .7 .5 o .9 .5 .6 .0 .5 .6 0 .9 .5 .5 .6 o .8 .5 .5 .5 0.8 .5 .5 P- 120^ 104 108 104 108 120 104 127 104 108 121 104 108 104 129 121 108 104 104 109 122 131 104 109 104 123 104 109 133 104 no 123 104 104 no 124 104 no 104 124 104 no i66 Publications of the Shadows of THE bATELLI TES IE rHKi , UlUNt, , /c«i Crossing the minor axis of the disk at the distance y from th< 1908. Gr. M. T y 1908. Gr. M. T. y July I. Te. 14^.3 4^.5 North Au. 10. Te. 5^8 5^4 Rh. 14 .5 6 .8 Di. 17 .1 6 .1 3- Di. 9 .4 5 .3 II. Rh. 6 .6 8 .0 Te. II .6 4 .5 12. Te. 3 I 5 .5 5. Te. 8.9 4.6 13. Di. 10 .8 6 .2 6. Rh. 3 .0 6.9 14. Te. 0 .4 5 .5 Di. 3 I 5 .3 15. Rh. 19 .0 8 .1 7. Te. 6 .2 4 7 Te. 21 .7 5 .5 8. Di. 20 .8 5 .4 16. Di. 4 .5 6 .2 9- Te. 3.6 4 7 17. Te. 19 .0 5 .5 10. Rh. 15 .4 7 I 18. Di. 22 .2 6.3 II. Te. 0 .9 4 -8 19. Te. 16 .3 5.6 Di. 14 .5 5 .5 20. Rh. 7 .4 8 .2 12. Te. 22 .2 4 .8 21. Te. 13 7 5 .6 14. Di. 8 .2 5 .5 Di. 15 .9 6.3 Te. 19 .5 4 .9 23. Te. II .0 5 .6 15. Rh. 3 .9 7 .2 24. Di. 9.6 6.4 16. Te. 16 .8 4 -9 Rh. 19 .9 8.3 17- Di. I .9 5.6 25. Te. 8.3 5 .6 18. Te. 14 .1 5 0 27. Di. 3 .3 6.4 19. Rh. 16 .3 7 .3 Te. 5.6 5 7 Di. 19 .6 5 .6 29. Tc. 2 .9 5 7 20. Tc. 11 .4 5 .0 Rh. 8.3 8.4 22. Tv. 8 .7 5 I Di. 21 .0 6.5 1 Di. 13 -3 5 7 31. Te. 0 .2 5 7 24. RIi. 4 .8 7 -4 Sept. I, Di. 14 .6 6.5 Te. 6 .0 5 .1 Te. 21 .5 5 7 25- Di. 7 0 5 .8 2. Rh. 20 .8 8 .6 26. Tc. 3 -3 5 .2 3. Te. 18 .8 5 .8 28. Tc. 0 .6 5 2 4- Di. 8 .4 6 .6 Di. 0 .6 5 ■« Tc. 16 .1 5 .8 Rh. 17 -^ 7 .6 7. Di. 2 .0 6 .6 20. Tc. 22 .0 5 -3 Rh. 9 .2 87 30. Di. 18 .3 5 -9 Tc. 13 .4 5 .8 31. Tc. 19 -3 5 -3 9. Te. 10 .8 5 .8 Aiifj. 2. Rh. 5 -7 7 7 Di. 19 7 6 .6 Di. 12 .0 6 .0 ri. Te. 8 .1 5 .9 Tc. 16 .6 5 -3 Rh. 21 .7 8 .8 4- Tc. 13 -9 5 -4 12. Di. 13 .4 6.7 Di. 5 -7 6 .0 T3- Tc. 5 .4 5 9 6. Tc. 11 .2 5 -4 1.=^. Tc. 2 .7 5 .9 Rh. 18 .1 7 .8 Di. 7 I 67 7- Di. 23 -4 6 .1 17. Tc. 0 .0 5 -9 8. Tc. 8 .5 5 -4 18. Di. 0 .8 67 Astronomical Society of the Pacific. 167 1908. Sep. 18. Te. 20. Di. Tc. 22. Tc. 23. Di. 24. Te. 26. Di. Te. 28. Te. Di. 30. Te. Oct. I. Di. 2. Te. •3. Te. 4. Di. 5. Te. 7. D: Te. 9. Tc. Di. 11. Te. 12. Di. 13. Te. 15. Te. Di. 17. Tc. 18. Di. 19. Te. 20. Di. Te. 22. Tc. 2^. Di. 24. Tc. 26. Di. Tc. 28. Tc. 29. Di. 30. Te. 31. Di. Xnv. I. Te. 3. Te. Di. 5. Te. 6. Di. Te. 8. Te. 9. Di. Gr. M. T. 2I^3 18 .5 18 .6 15 12 13 5 .9 .2 .2 .9 10 .5 7 -8 2^ .6 5 .2 17 2 23 .3 .5 .8 II .0 21 .1 4 18 •7 .4 15 -7 22 .4 13 .0 16 .1 10 .3 7 .6 9.8 5 .0 3 -5 2 .3 21 .2 23 .6 20 .9 14 .9 18 .2 8 .6 15 .5 12 .8 2 .3 10 .2 20 .0 7 -5 4 .8 13 7 23 20 I .7 .1 .4 .4 •7 .1 S^.g North 6 .8 5 -9 5 .9 6 .8 5 .9 6 .8 6 .0 6 .0 6.9 6 .0 6 .9 6 .0 6 .0 6.9 6 .0 6.9 6 .0 6 .0 7 o 6 .0 7 .0 6 6 .1 I 7 .0 6 .1 7 6 .0 .1 7 I 6 .1 6 .1 7 .1 6 .1 7 I 6 6 7 6 7 6 6 .2 .2 .1 .2 .1 .2 .2 7 I 6 .2 7 .2 6 .2 6 .2 7 .2 1908. No. 10. II. 12. 14. 16. 17. 18. 19. 20. 22. 25 27. 28. 29. 30. Dec. I. 3. 5. 6. 7. 9. 10. II. 12. 14. 16. 17. 18. 20. 22. 24. 25- 26. 27- 28. 29. 31. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Te. Di. Te. Di. Te. Gr. M. T. 1 8^.0 18 .8 15 .4 12 .5 12 .7 10 .0 6 .2 7 .3 2^ .9 4 .6 I .9 17 .6 23 .3 11 .3 20 .6 17 .9 5 o 15 .2 22 .7 12 .5 9 .8 16 .4 7 .2 10 .1 4 .5 1 .8 3.8 23 .1 21 .5 20 .4 15 .2 17 .8 15 I 8 .9 12 .4 2 .6 9 .7 7 .0 20 .4 4 .4 14 .1 I .7 23 .0 7 .8 20 .3 I .5 17 .^ 6".2 North 7 .2 6.3 7 -2 6.3 6.3 7 .2 6.3 7 -3 6.3 6.3 7 .3 6.3 7 .3 6 6 •4 .4 7 .3 6.4 7 6 .3 .4 6 .4 7 .3 6 .4 7 .3 6 .4 6.4 7 .3 6.4 7 .3 6.4 7 .4 6.4 6.4 7 .4 6 .4 7 .4 6.4 6.4 7 .4 6.4 7 .4 6 .4 6.4 7 .4 6 .4 7 .4 ^ A 1 68 Publications of the 1909. Gr. M. T. y 1909. Gr. M. T. y Jan. 2. Te. 15^0 6" A North Jan 16. Di. ii»».8 /'.S North Di. 19 .2 7 .4 17. Te. 17 .5 64 4- Te. 12 .3 6.4 19. Di. 5 .5 7 .5 5. Di. 12 .9 7 .4 Te. 14 .8 6.4 6. Te. 9.6 6.4 21. Te. 12 .2 6.5 8. Di. 6 .6 7 .4 Di. 23 .2 7 .5 Te. 6.9 64 23 Te. 9 .5 6.5 10. Te. 4 .2 64 24. Di. 16 .9 7 .5 II. Di. 0 .3 7 .4 25. Te. 6 .8 6.5 12. Te. I .6 6.4 27. Te. 4 .1 6.5 13. Di. 18 ,0 7 .5 Di. 10 .6 7 .5 Te. 22 .9 6.4 29. Te. I .4 6.5 15- Te. 20 .2 6.4 THE CORONAL SPECTRUM AS OBSERVED AT THE FLINT ISLAND ECLIPSE. By W. W. Campbell and Sebastian Albrecht. Two single-prism spectrographs were designed by Mr. Campbell for efficiency in recording the continuous spectrum of the corona. These and a three-prism spectrograph, referred to below, were mounted on one clock-driven polar axis. All were adjusted by Mr. Alrrfxht, assisted by Mr. Merfield, and the programme of observations at the time of the eclipse was carried out perfectly by Mr. Merfield. The slits of the three instruments extended east and west centrally across the Sun's image. One of the single-prism instruments, using a Seed plate No. 27, was exposed from o™ 5" to 3™ 5i*. The spectrum of the extreme inner corona is recorded from A 3550 to A 5390. It is very strong for the first 2' from the limb ; the intensity falls off gradually out to a distance of i5'-20' from each limb; and the intensity is then nearly uniform out to the ends of the slit, 49' on the cast side of the Sun and 40' on the west. A continuous spectrum covers the region corresp>onding to the Moon, the intensities near the ends of the slit being slightly less than over the Moon. Astronomical Society of the Pacific. 169 A brilliant prominence on the east limb is the origin of a great numlwr of overexposed bright lines. The following prominence lines are lengthened by the diffusion of the light in our atmosphere; their extent, measured from the east limb of the Moon being; — East 20', West 20' A 49 H{+!h) 49 m 49 Hy 40 X447I 30 Hp 49 72 Full length of slit, strong. -,3 ■' '■ " " " 33 +, Ends in west coronal spectrum. 33 +. 30 Very faint. 33 +, Ends in west coronal spectrum. A longer slit would no doubt have given still greater extent to the lines now limited at 49' and 72'. The H and K calcium lines, especially, terminate abruptly at the points on the plate corresponding to the slit-ends. The green bright line at A 5303 and a bright line at A 3601.3, the latter apparently new, are recorded in good strength, each out to 3' from the west limb and 2' from the east; the coronal hnc measured at A 3987.0 is faintly visible, apparently length- ened by diffusion, on the strong continuous spectrum; the well-known coronal line measured at A423I.S is easily visible, extending by diffusion entirely across the Moon and to the ends of the slit ; a faint line at A 3625.5, showing on both sides of the Sun, is short, but apparently a new coronal line: a faint line, visible on both sides, at A 3643.3, and a more diffi- cult line, showing only on the east side, at A 3801.0, are proba- bly coronal lines that have been observed before; a line 2' long, showing only on the east side, at A 3641.3, is of doubt- ful reality, and all other coronal bright lines appear to be lost in the strong continuous spectrum, the dispersion being low. The spectrum of the inner corona seems to be free from absorption-lines, at least out to 8' or 10' from the limb. The absorption-hnes show very faintly in the spectrum of the outer corona, and still more faintly fand doubtfully) in the Moon's area, especially in the region A 3900-4500. They are most readily obser^'ed in the regions lying between 10' and 20' from the limb. The maximum intensity of continuous Publications of the spectrum, estimated to lie at A 4675. seems perceptibly further to the. red than the iTiaximum on the solar spectrograms obtained with the same instalment at Mt. Hamilton, — signifying a lower effective tenlperature in the corona than in the Sun. Cramer isochromatic instantaneous plates were used with the other single-prism instrument. One exposure, from o" 3* to o" 20", recorded nothing, no doubt on account of the clouds then prevailing. Another exposure, from o'" 30" to 3° 51". recorded the coronal spectnmi very strongly. The spectrum for the inner corona extends from X 3600 to A 6000, all in good focus. The above description of the coronal spectrogram on the Seed plate applies in general to this spectrogram, taking its isochromatic character into account. The slit extended 47' east of the Sun's image and 35' west. The hydrogen and calcium lines of the prominence are likewise lengthened by diffusion, the H and K lines of calcium extending the full length of the slit, — 47' east and 68' west from the prominence; the merest trace of an absorjition si>ectrum is visible likewise in the mid-coronal region, and only in the violet. The intensi- ties in the regions near the ends of the slit are clearly less than over the Moon, The green coronal line, measured at A 5301,4 it 0.5, is strongly recorded, certainly to 20' on the west and 15' on the east. However, as this line is easily visible across the Moon's area, the great lengths are doubtless due in large measure to diffusion in our atmosphere. The bright coronal line at A423i.2±o.2 is also recorded as of great length, especially on the west side. A 3986.9 ± 0.2 is long but very difficult. A number of other coronal lines are su5i>ected, but the strong background of continuous spectnim renders their existence uncertain. The dispersion being low, the wave-lengths assigned above are subject to slight error. The interpretation of these spectrograms is a difficult mat- ter, as the subject is more complex than it at first seems. There can be little doubt that the coronal spectrum combines three types :^bright-line, continuous, and dark-line. It fur- ther seems clear that each poiitl of the slit receives light, by diffusion, from every prominence, from every point in the uneclipsed chromosphere, and from every point in the corona. Astronomical Society of the Pacific. If the H and A' calcium light is diffused in our atmosphere to cover the slit strongly to a distance of at least 72' from the east limb, the apparent center of the effective diffusion, the brilliant light of the entire inner corona must by similar dif- fusion fall upon the entire length of the silt. We believe that this diffused inner-coronal light is chiefly responsible for the spectrum corresponding to the ends of the slit, and to that part of the slit covered by the Moon's image, and that ordinary sunlight diffused in the air in front of tlie instrument, from the illuminated atmosphere outside of the Moon's shadow, has contributed very little to the recorded spectrum. Thus the spectrum covering the Moon's section, neglecting diffused prominence and chromospheric radiations, is almost wholly a coronal spectrum. If it were in good part due to photospheric light, the absorption spectrum would be conspicuous : and the same could be said for those areas of the spectrogram corre- sponding to the ends of the slit. In fact, the true spectrum of the outer corona, say beyond 20' from the limb, is either not recorded at all, or is masked by the superposed spectrum due to diffused light from the brilliant inner corona. It was remarked by the observers with previous experience — Messrs. Perrine. Abbot, and Campueu. — that the outer corona, as viewed by the naked eye. was disappointingly faint. The proportion of light radiated by coronal particles appears to have been relatively large, and the sunlight diffused by the coronal particles relatively small, on this occasion. It appears that only in the region of the plates corresponding to the middle corona are the proportions of radiation spectrum, ab- sorption spectrum (sunlight), and diffused inner-coronal spectnmi such as to let the faintest traces of absorption -lines be detected. We do not feel that these facts militate against the theory of the corona held for several years by the Lick eclipse observers. Whether the stronger absorption spectra, observed in Sumatra in 1901 and in Spain in 1905 indicate a variable coronal spectrum or the influence of the thin clouds over the corona in 1901 and 1905. is a question for future consideration. A spectrograph of high dispersion, containing three ex- tremely dense glass prisms, was used in the hope of recording the green coronal line, in order to determine its wave-length 172 Publications of the with great accuracy. The solar spectrum was impressed upon the plate immediately after the end of the total eclipse, for reference. No trace of the coronal line exists on the plate, undoubtedly because of the strong absorption of the prisms. TABLES OF THE ELEMENTS OF COMET-ORBITS, JANUARY, 1896, TO DECEMBER, 1907. By J. C. Duncan. The following tables have been prepared at the suggestion of Director Campbell, to supplement those compiled by W. C. WiNLocK, and published in Publications of the A, S. P., Vol. VIII, p. 141. Professor Winlock's tables include all the comets whose orbits were known and which reached peri- helion before January i, 1896; the tables here presented complete the list up to the present time. The data were derived from the various astronomical period- icals, chiefly from the Astronotnische Nachrichten and the Astronomical Journal. In each case that set of elements was chosen which most nearly represented the path of the comet. Table I p^ives the elements of comets in order of perihelion passage. The numbers in the first column are continued from those of Win LOCK, which are identical with the numbers in Dr. Galle's catalogue of comet-orbits. The second column contains the designation of the comet according to the order of its discovery; in the case of well-known periodic comets this is followed by an abbreviation of the name of the comet's discoverer. These abbreviations are as follows: — d'A = d'Arrest Ho = Holmes Bk ~ Brooks To = Tempel (second comet) E = EnCKE Tu = TUTTLE F = Faye W = Winnecke Fi = FiNLAY Wo = Wolf The third and following columns give the orbital elements, as follows: — Astronomical Society of the Pacific. 173 T = time of perihelion passage, expressed in Greenwich mean time. 90° the mo- tion is retrograde). q z= perihelion distance, in astronomical units. a =^ semi-major axis of the orbit, in astronomical units. U = period of revolution about the Sun, in years. e = eccentricity of the orbit. The eleventh column gives the names of. the discoverers of new comets, and the last column contains remarks pertaining to the comets or their orbits. In order to facilitate the comparison of the orbits of newly discovered comets with those already known, the comets given in Table I are rearranged in Tables II to V, in the order of magnitude of their various elements. Each comet is there indicated by the number applied to it in Table I, or, in the case of the periodic comets, by the abbreviation of the discoverer's name. In these Publications, Vol. XIV, p. 49, Professor Hussey extended Winlock's Table I to January, 1902; but as he did not extend the other tables, the elements of those comets are reprinted here. Hussey's values of the elements do not differ materially from mine. Since this list contains few periodic comets not given in Winlock's list, no classification was made in the order of a, U, or e. 174 Publications of the u B Ok 00 00 u •S? u a u • M > o t S5 § .S M ;: w < > pi< 1^ ^ 0^ c/) c/) O • hi ^ 1^ (X4 ^ tt \n o ^i d 6 Pi o ::i ?^ IT) O K c^ iz: HH • o Tj- lO Q • • CO ^ ^ < Oi Pi < 88 00 ^ CS '^t C- \ri *>"?"! "^ r/) 6 1-^ O "^ ^^ H o •«• CO \n — »o5c •- U ^i^ t-H ^ X ^ c ^ U Lo P o i>. "^ Q\ J r^ ^ 1-4 l-l H^ oa < H fs IN. q lo -5 00 '- 1-1 •-• c^ •4 w W H M u u w do d o \0 i>»vd vd to ■^ ro C\ o ^ " t^ ^" (r;Nd «r. O 00 O nQ nC' ^\ CM ^ oc a\ -^ «_ 00 C^ |_, 1^ 1^ 0^ aa O u < \n\o \n N- "^ lO 6 6 6 o «^ If ^ ^ ^ «■ 6 d -*' -' "^ q o. fN 00 1^ I— ^ ^4 vC at M 2 O H O M ** M ** M a 2 « Q < at O K w «( O 0^ U U 0k CQ CM O - » • • • • • w K s 36 >! 36 oa »4 oa . O H O J o « G 5 < S < o u n c s ■ o to c^ CI "* :: IN. '^ -^5- ro O a\ CM CO • • • • . - « o o o CMX'^t^C^ ^CtOQCov ■T -^ lO — t>» icoxt'^ -^OOOO'^^ Ot^l^r'iCM CM d "^vd oc vo O <^ O r> 01 I-. CO CM fM 0\ Tf »o Tj-vn to 1^ 0\ CO On CM to •-> CN •- rM fO ^ '-' CM CM PON «. "1- O On '^ to ro -^ *00 t^ CM vq fovq Tt-vq »o po "^ '^i f*b O <^ vo CM ?i CM « "-• t^ ^ 00 N- Qv oc -^vd to d h^ OOO '-' VQ ^ >-l 1-4 (\| ■^vO CO CO « - O vO 00 00 dob CN ov Tj- "^ CM O. O <^ CO i-i KI CO i-H Tf O O O CO CM to CO "^ C^ HH t>» GOO ■-• CM "-I 00 cOvD C\ O '-'* d^ f>. d vd CO »- I— I fi fv^ CM \0- ^ OnvO "^ -rod «^od cj r^, 'T "^00 vO to 1^ d K Tt- to ►- CM CM CM 'N O CM to CN "^ ^ 6 6 f^ 1-1 ►- fV| CM CM o .- .- lo o f'Soc 'too to i-i 'N i-t CM I-" CM CM tT CO tT 00 <^ i-I "^ to CM CM ►^ I— ^^, < t— »o ;:: > ^ >» o o c -r ^ I' r; n f- 1—1 •— • f!^ <4 f=^ t— it— > hr ••-' ■*-• • b» «- i: -_b a. < < ^, ^rc/i 'ImI" I'I'I^I^I^ ;'-g^^ X O « CM fO -^ .'Sn'Sn O^ On Vj fc^"*-. G -Ci too r^X On - r, 'Nj c^ A^ t -r -r T '4 00 00 00 00 ^ CN 0\ Cn^ ^ ':3 "^ be O ^ '^1 CO T CO CO «^^ ^< "^ t -t -t ^ -t 3C 00 95 00 ^ 0» Ov Ov On 'i- u '—^-c; ■•* tovO 1^00 On CO CO CO CO CO -t -^ n ^ '«* J^ 0> 0\ Ov 0\ Q -O Vj C -O tOVO r^*OQ On Astronomical Society of the Pacific. 175 c . o c o ■*- c t ''- tn ^ 5? CCCQ us to u Xi v> a* ki V c O tn C o > ki •c S en C V E ki ca c 8 u 0^ us w 2 i 2 • =2 2 S * o « o o c o o< u u o « « < < « « u » » e C CU w 'w Grigg. borrelly Brooks. GlACOBINl BORRELLY GlACOBINl KoPFP. SCHAER. Brooks. GlACOBINl Ross. 0 "Soovo On 0 0 d 0 0 0 t^ 10 CO K g s «*; c^' cs «o 21 a. o c o « £ » H J O " Li w a IS S H 'O d Si p * • • • o 000 rx cs <^ S8 \0 vOvO vO <0 moo ^ I o W to d CQ o ►J i^ s^ "J M < 5 W s o a s }■ >o "^ Tt- In. Tf CO o ^^oq oj c^ fo •-: ^^ o c5 ci w h^ vO Osvq ^ p On c< ) d d d cs d d "^ -.pQ • • o o irj "^ ^ On Ov VC 00 vd d fO \3 — LO PO -^ \o i/Snc 10 On .H^N-irits. cioqqr> n OC <^ «^ »o "-• ir -. 00 >r; C. 00 vO »'^ ^. - - . - c^ K On '^^ rx «o food looc "-• "^vo Kci (sivQ^ci*^* <«om*c6'3'K dvd^rj lO^t ■-• i-iOv^tNN- CScor>.iO"T ClOQOvts.fO vo»n o^oo Ov OO VC ^f OnT^ocot o^T^MOM ci »M* CO M* CO "^ K ►^ O QvO dv d CO Tj- 00 VO Tf ir> ■^ ts. On ts. O 00 o Tf 00 *oco rxoNcs'-' r>.r>.cots.co moo ■-• vo m go o -^ m >0 C< (S covO lOts.cocO'- tO-rfMOOON MOv OOO "^ OMiO xooo «N 00 On ^f "^ CviOn»OCO OOMTfiO'tf 0000>O"^"^ COOO ONtN»-i 1-1.-10 '-' sOI'^»OM n-COtJ-n-m \OMO»0 tN o fo\o CO loiNN-ts."^ Oi-ivOTrp locsw^"^ M rxvo ►^ On r>. •-' -^ "^ MM'-'M MCii-i i-i»_ta^ M MMNc|»h »mMm MCO •-• «5§|^ «^si«o' iiitt t3sc-g| ||tj|3 |&&g- S^S:SS :S r>. o o o av--Cit3"0 •C>U*X30"0 'o-O^O-O •OO'oVjVfc.^ ta'^-CSbfiQ -O'o'XS^ o .-I M CO -^ invo rxoo On Q .S 2 <^ S" mvQ rxpo q\ o « ^ ^ '^ '4>^ \^^ loioiomio loioirjioio vO >0 O nO^ vo^O'OvOvO t^ts^t^t^^t^ \:!i.^y:i.^ -^ "^ Tf Tf Tf -^ "^ Tf -^f Tf "^ "^ "Tf rf "Tf "^ "^ "^ Tf "n- n- n"^ "^ "^ -^ '^ '^ '^ 176 Publications of the Table II — Comets Arranged in Order of w. CD Numbers > (i> Numbers. 0** to 10** 422, 437, 454, 473, 440 180** to 190® E. T., 455 10 20 444, 446, Ho, . 470 190 200 467 20 30 434,445 200 210 F, 448, 472, 435, Tu 30 40 476 210 220 40, 50 423, 459 220 230 450 50 60 458 230 240 436 60 70 429 240 250 70 80 • 250 260 80 90 466 260 270 90 100 270 280 468 100 no 280 290 no 120 290 300 451, 477. 478 120 130 439, 456 300 310 130 140 465, 453, 424 310 320 Fi, 472, 474 140 150 430 320 330 475 150 160 452,464 330 340 160 170 438,426 340 350 Bk 170 to 180 427, Wo, d'A, w. 447 350 to 360 462, 463, 420 Table III — Comets Arranged in Order of Q. Q. Numbers. Q Numbcn I. o*' toio** 453 180° to 190*' 475 10 20 Bk 190 200 424. 447. 472 20 30 440 200 210 420, F, Wo 30 40 429, 438 210 220 451, 455, 459 40 50 445. 452 220 230 465 50 60 450, Fi, 478 230 240 60 70 240 250 426 70 80 468, 436, 462 250 260 435 80 90 473. 427 260 270 Tu, 430, 470 90 100 437, 439, 467, 474 270 280 434. 444, 458 100 no w, 448 280 290 466 no 120 454 290 300 456 120 130 T, 300 310 130 140 310 320 140 150 477, d'A 320 330 446 150 160 423. 463 ,^30 340 432, Ho, E 160 170 476 340 350 464 170 to 180 /1 22 350 to 360 Astronomical Society of the Pacific. 177 Table IV — Comets Arranged in Order of i. • f Numbers. t Numbers. 0** to 10** Bk, 464, 470, Fi, 477 90** to 100** 459 ro 20 F, 424, 426, d'A, W, 100 no E, T,, 451, 472. 476 no 120 475, 478 20 30 Wo, 437, 438, Ho 120 130 458, 466 30 40 447, 453, 462 130 140 448 40 50 454, 463, 467 140 150 427, 439, 440, 445, 50 60 422, Tu, 473 465, 474 60 70 429. 436, 446, 450, 455 150 160 420, 452 70 80 430, 435, 444 • 160 170 434 Soto 90 423, 456, 468 170 to 180 Table V — Comets Ari lANGKl) IN Order of q. Q Numbers. Q Numbers. 0.0 to 0.2 1.4 to 1.6 424,434 0.2 0.4 E, 440, 448, 456, 467 1.6 1.8 F, Wo, 436, 444, 470, 0.4 0.6 420, 422, 438, 450, 451, 472 452, 453, 455, 477 1.8 2.0 Bk, 459 0.6 0.8 435, 439, 468 2.0 2.5 437, Ho, 474 0.8 1.0 W, 447, Fi, 475, 478 2.5 30 454,458 1.0 ,1.1 427, 430, Tu, 446, 465 3.0 4.0 464 i.r 1.2 423, 426, 463 > 4.0 1.2 1.3 T,, 466, 473, 476 1.3 to 1.4 d*A, 429, T,, 445, 462 178 Publications of the PLANETARY PHENOMENA FOR JULY AND AUGUST, 1908. By Malcolm McNeill, PHASES OF THE MOON, PACIFIC TIME. First Quarter. July 6, I2*> 25™ p.m. Full Moon " 13, I 48 p.m. Last Quarter.. . " 20, 4 2 a.m. New Moon " 27,11 17 p.m. First Quarter. .Aug. 5, i** 40™ a.m. Full Moon " 11,8 59 P.M. Last Quarter.. . " 18, i 25 p.m. New Moon " 26,2 59 p.m. The Earth reaches its greatest distance from the Sun on July 2d at about 11** a.m., Pacific time. Mercury is not in good position for naked-eye observation during July and August. It is an evening star on July ist, but is very close to the Sun, and passes inferior conjunction on July 4th, becoming a morning star. It then moves away from the Sun toward greatest west elongation, reaching that point on July 25th. The planet's apparent distance from the Sun is then 19° 51', — a much smaller greatest elongation than the average because it occurs less than four days after peri- helion. It then rises a little less than an hour and one half before sunrise, and may be seen in the morning twilight for a few days. It then moves out toward superior conjunction, reaching it on August 20th, and becoming an evening star, but does not reach a sufficient distance from the Sun to be seen in the evening twilight before the close of the month. Mercury is in conjunction with Venus on July 15th, with Neptune on July 28th, with Jupiter on August i8th, and with Mars on August 20tli, but none of these conjunctions can be observcrl with the naked eye on account of the proximity of the planets to the Sun. J^enus on July ist is, like Mercury, an evening star, very close to the Sun, reaching conjunction and becoming a morn- ing star on July 5th. The distance between Sun and planet increases very ra])idly. so that by August ist Venus rises con- siderably more than two hours before sunrise, and bv the end of the month the interval is a little more than three and Astronomical Society of the Pacific. 179 a half hours. The planet will reach its greatest west elonga- tion before the middle of September. The planet will again be very bright in late July and early August, reaching the maximum on August iith. As in the previous May, it will then be bright enough to be seen by the naked eye in full sunlight. It is not easy to find, but when once seen in day- light it seems so conspicuous that one wonders at the difficulty in finding it. It is easiest picked up when the sky is clear but partially covered with drifting clouds. One can keep his eye on a rift in the cloud as it gradually passes over the place where the planet is known to be, and thus find the planet more easily than he can when there is no cloud. Mars is too near the Sun throughout July and August to be easily seen. It is still an evening star on July ist. and then sets only about an hour after sunset. As the planet by this time has gradually faded away to about the brightness of the pole-star, it will not be an easy matter to see it in the evening twilight. The distance between Afars and the Sun gradually diminishes until conjunction is reached, on the night of August 21st, and the planet becomes a morning star. The distance between Sun and planet then increases, but does not become great enough to permit the planet's being seen in the morning twihght until some time after the end of the month. At the time of conjunction with the Sun the distance of Mars from the Earth is 248.000,000 miles. This is more than 10,000,000 miles greater than it is at an average conjunction, since both the Earth and Mars are at nearly their maximum distance from the Sun, the Earth having passed aphelion on July 2d, while Mars will be in aphelion on September 3d. At the last oppo- sition, in July, 1907, Mars was near perihelion while the Earth was in aphelion, but both were then on the same side of the Sun, and they were much nearer together than at an average opposition. The same thing will occur at the next opposition. late in the summer of 1909. Jttpiler sets at about 9" 30" p.m. on July ist, about two hours after sunset, and may be easily seen in the evening twilight, but its apparent distance from the Sun is lessening rapidly, so that by the end of the month it is only about 12" distant and it sets only forty minutes after sunset. As it is one of the brightest of the planets it may possibly be seen close ta \V«, i8o Publications of the Astronomical Society, &c. horizon about half an hour after sunset, but only under the best of atmospheric conditions. Conjunction with the Sun occurs on August 17th, and the planet becomes a moming star. By the end of the month it has moved far enough away from the Sun so that the conditions of visibility are a little better than they were at the beginning of the month. Saturn rises at about midnight on July ist, and at about 8^ P.M. on August 31st. It is in the constellation Pisces, and moves slowly eastward until July 23d, and then begins to move westward; but the whole motion is only about i^, an amount hardly noticeable, as there are no bright stars nearby so that small changes in position can be marked. As seen in the tele- scope, the rings appear about as they did during June, but the Earth in its annual motion begins to draw nearer the plane of the rings during August, and there will be slight narrowing, which will continue until December. Uranus comes to opposition with the Sun on July 7th, and will then be above the horizon throughout the entire night By the end of August it sets at a little before i"* a.m. During the two months' period it moves about 2® westward in the constellation Sagittarius, and is about 5® north of the most eastern star in the bowl of the "milk-dipper," not far from a line between that star and ir Sagittarii, and nearer the latter. Neptune comes to conjunction with the Sun and becomes a moming star on July 6th. It remains in the constellation Gemini, NOTES FROM PACIFIC COAST OBSERVATORIES. Recent Double- Star Literatltre. The most important of the recent publications relating to double-star astronomy is the "Catalogue and Remeasurement of the 648 Double Stars Discovered by Professor G. W, Hough," issued as Volume III, Part III. of the Astronomical Series of the Publications of the University of Pennsylvania. The author is Professor Eric Doolittle, who has in this volume done for the Hough stars what Burn ham, Hussev, and Lewis had previously done for the Burnham, Otto Struve, and Struve stars, respectively. Professor Doolittle's plan involved a complete remeasure- ment of all the stars discovered by Hough. This was begun in 1901, and practically completed within the next two years. The Hough stars, however, include a number that are very close pairs, and hence exceedingly difficult to measure with an iS-inch telescope. There are also sixteen pairs that have never been seen double since Hough listed them. The stars in these two classes, especially the latter, required careful watching for a number of years before satisfactory measures could be seaired or the definite statement made that the star was single at the present time. The work as it now apjiears is very satisfactory from every point of view. The measures have been made in the careful and thorough manner that has characterized all of Doolittle's work, and the arrangement of the results is convenient, and enables the reader to gather quickly all extant information regarding any star. ' In his Introduction, Professor Doolittle comments on the comparatively few measures that have hitherto been made of the Hough stars. Only twenty-three of them have been meas- ured more than five times, 494 have been measured by Hough only, and sixty-six of these on only one night. It nj^s, •Cwoa obvious that systematic renieasuremeiit was urgently demanded. As inight have been expected, however, the new measures have revealed orbital motion in comparatively few pairs. This is mainly due to the fact that none of Hough's discoveries date back thirty years, his first list, containing 209 pairs discovered between iSSr and 1886, having been published in 1887; and some are more recent than 1898. That a large percentage will ultimately show orbital motion cannot be doubted, for nearly four hundred of the Hough pairs have distances under 5", and the probability that such pairs are binary systems is so great as to amount to practical certainty. It will take a long time, however, for the orbital motion to become evident, and careful examination of the volume before us indicates that it will be unnecessary to remeasiire the greater number of Hough stars for another quarter of a century. About 100 pairs, on the other hand, ought to be remeasured within the next few years, and fully half that number should be closely watched. The most interesting star in the catalogue is 13 Celt =^ Ho 212, on the rapid motion of which the present writer has commented in earher numbers of these Publications.' Professor Doolittle has computed the orbit of this pair with results that are in satisfactory agreement with my own. the two revolution periods being 7.42 and 7.35 years. Among other publications of interest to double-star observers we note the new series of articles on "Double-Star Astron- omy" now appearing in The Obscn'aiory. In 1893 Mr. Thomas Lewis, of the Greenwich Observatory, published a series of papers with the same title in the same journal. The present series, which befjan in the February (1908) number, is a second edition, revised and brought up to date. The general reader as well as the specialist will find much to interest him in these articles. In the Astronomische Nachrichten, No. 4229, Dr. W. A. DoBERCK publishes a paper entitled "On the Accuracy of Meas- ures Made by the Principal Douhle-Star Observers," in which he gives the results of comparisons of observations with posi- tions computed from the orbits of thirty binaries which he has lately investigated. The paper is a very interesting one. and brings out clearly several important points. The first is that the probable errors of measurement are in general very sm 'S« Vol. XVII., pp. 16 and ijg; \ Astronomical Society of the Pacific, 183 seldom exceeding o''.05 in either angle or distance. In the second place, it is evident that the size of the error is influ- enced by the relative magnitudes of the two components, and also by their angular separation. The interesting point is developed that the probable error of angle measure, as well as of distance measure, in general increases with increasing distance, within the limits investigated. In another number of the same journal (4235), Dr. Doberck continues his study of binary stars with an orbit of y Virginis. It may be added that Dr. Doberck has recently established a private observatory near London, in England, and has resumed the active observation of double stars in addition to his mathematical researches. Rev. T. E. EspiN continues his work on double stars with unabated enthusiasm, as is evident from his "Fifth Series of Measures of Double Stars" and "A List of 109 New Double Stars," which are published in the Monthly Notices R. A. S. for January, if^. Of the new pairs five are under 2'' and the majority under 10'', though a number of wider pairs are included. The desirability of listing the wider pairs as double stars seems questionable to the present writer. The only object it can have is to call attention to these pairs in the hope that they will be measured, and whatever relative motion may exist be thus brought to light. But experience has demonstrated that relative motion is very slow, even in the moderately close pairs — those from 2" to 5''. Would it not be wiser to concentrate the energies of micrometer observers upon these and closer pairs, leaving the motion in the wider pairs to be discovered by photographic methods? The same number of Monthly Notices contains orbits of the binaries pSo, )3 5i3, and )3 552, by Dr. T. J. J. See. These are all of interest, and will serve to call new attention to systems that ought to be measured every year or two. The observations of the next ten or fifteen years should furnish data to improve these first approximations to the elements. Double-star observations occasionally appear in unexpected places. Thus the "Katalog von 10663 Stemen." just published as No. 10 of the New Bonn Observatory Publications, by Professor F. Kustner, gives, on pp. 79-94, a list of micro- metric measures of double stars and companion stars within i' 184 Publications of the detected during the course of the meridian-circle observations. Only such pairs have been measured as had not been adequately measured elsewhere. R. Q. Aitken. May 22, 1908. Progress on the Crossley Eros Solar Parallax Work. The work of determining the solar parallax from the photo- graphs of EroSj taken with the Crossley reflector in 1900, is almost completed. The plates which were selected for use have all been measured and reduced by Mrs. Moore (nee Chase) and Miss Hobe. For some months now a discussion and comparison of the results has been in progress. This discussion is nearly completed, and it is hoped soon to send the manuscript to the printer. While the final parallax has not yet been derived, it can be said that it will hardly differ o".oiO from 8".8oo. Mt. Hamilton, May 21, 1908. ^* ^- PeJ^^NE, Recent Observations of the Moving Object Near Jupiter, Discovered at Greenwich by Mr. J. Melotte. After the receipt of the telegraphic announcement of the discovery of this object, early in March, Dr. Albrecht ob- tained some photographs of the region with the Crossley reflector, on the nights of March 7th, 8th, and 9th. The new object (as well as the sixth and seventh satellites) is shown on the plates of March 8th and 9th. A position obtained on March 8th has been published. Photographs have been obtained by the writer on March 24th, 27th, 31st, April 1st, 28th, and 29th, on which the Green- wich object, the sixth and seventh satellites are shown. The following positions have been derived from the photo- graphs of April 1st and 29th: — April, 1908. Id 8" Sim o« P. S. T. a 1908.0 8h 26"^ 458.58 « I908.O -f-IQ** 49' 27"^ 29 8 51 15 8 33 44 .22 4-19 35 49 -O In brightness, the new object diflfers but little from the seventh satellite. From a preliminary discussion of the observations from January 27th to April 3d, the Greenwich astronomers conclude that it belongs to Jupiter.^ * The Observatory for May, 1908, and A. N.. No. 4246. Astronomical Society of the Pacific, 185 Mr. Melotte is to be congratulated upon so important a discovery. It is all the more creditable because it comes in the line of regular, routine work in observing satellites photo- graphically, of which a number of valuable contributions have been published from Greenwich. It is also a credit to a climate which has the reputation of being unsuited to the exactions of large telescopes. C. D. Perrine. Mt. Hamilton, May 21, 1908. Measures of p 208. Dr. See has recently called attention to this binary star, stating that it is now passing periastron, and that the relative motion is therefore very rapid and the companion perhaps invisible. The following measures, made with the 36-inch refractor, may therefore be of interest: — 1907.21 181 °.4 o".35 2' 1908.28 190 .0 o .39 I' ■n Comparing these positions with my measures in the two preceding years, viz: — 1905.18 167^.5 o".30 2° 1906.10 177 .3 o .30 5° it does not appear that the apparent motion is increasing in rapidity at the present time. It would seem that any estimate of the form of the orbit is premature. R. G. Aitken. May 22, 1908. Explanation and Correction. The two half-tone illustrations of the solar corona accom- panying my article, "The Crocker Eclipse Expedition of 1908," in the last number of these Publications, made and printed by an Eastern firm, were excellent in the proof-sheets supplied us, but so poor in the printed product that we regret having made another attempt to publish a corona in this manner. The engraver's printer has been the means of sadly misrepresenting this section of the expedition's work. An error was made, also, in orienting the half-tone block of the smaller corona (Frontispiece) : the side marked IV should have been marked ^. etc. W. W. Campbell. r were o I observF REPORTS OF OBSERVATORIES. LICK ODSERVATOHY, Ml". HAMILTON, CALIFORNIA. The last number of these Publications contains a full account of the Crocker Eclipse Expedition dispatched to Flint Island to observe the total solar echpse of January 3, 1908, It is therefore unnecessary, in this record of observatory activities in 1907, to refer to the subject, further than to say that the preparations at Mt. Hamilton and on Flint Island, and travel to the island, occupied the time of Messrs. Campbell, Perrine, AiTKEN. and Albrecht during the three or four closing months of the year. It is expected that the results of this very successful expedition will all be presented in these Pubticalions from time to time, as ready, in 1908. Professor Lewis, of the Department of Physics, University of California; Professor Boss, in charge of the U. S. Naval Observatorj', Pago Pago, Samoan Islands; Mr. Merfield, of the Sydney Observatory : and Consul and Mrs. Dreiier, of Papeete, Island of Tahiti, were valued members of the expedition. The observations with the meridian circle in charge of Astronomer Tucker, aided by Carnegie Assistant R. F, Sanfohd, were confined principally to the completion of two years' work on a programme for determining the accurate positions of stars based on fundamental methods. About 1900 observations on this programme were seaired during the year. The stars on the programme are distributed mainly between 37° north and 37° south declination. Special stars are included in the programme for the purpose of determining the ob- server's personal errors as affected by his position while making the observations, and by the direction of the apparent motion of the .stars through the field of view. Other stars for the investigation of atmospheric refraction effects were selected from 60° to 65° north declination, and observed at upper and lower culminations. These will give observed effects down to more than 80° zenith distance in the north, and selected southern stars having similar zenith distances were observed for the same purpose. The reductions of the observations for the two years are well advanced. Publications of the Astronomical Society, &c. 187 Mr. Tucker's problem is complicated by the existence of a daily period in the azimuth of the instrument, as shown clearly by both the first and the second year's observations. The meridian mark (mire) appears to give consistent results £or periods of considerable length, and the diumal azimuth varia- tions observed are clearly due to changes in the position of the instrument itself. It is only by making observations at all hours of the day that the azimuthal changes can be resolved into their component parts and the necessary corrections be applied to the observations. During the year, Volume X, Publications of the Lick Observ- atory, containing Professor Ti;cker's observations with the meridian circle obtained in 1901-6, was published and dis- tributed. The principal contents of the volume consist of a catalogue of 2798 zodiacal stars. The stars in the list were selected by Sir David Gill as a basis for heliometer measures of the Moon and planets. The volume also contains observa- tions of other special hsts of stars, as well as a discussion of the graduation errors of the circles. In the year 1907 a special list of stars was observed for Dr. L. DE Ball, of Vienna, for use in his determinations of stellar parallax. The right ascension of the Moon was observed on several nights in the fall and winter of 1907 to determine the effect of existing errors in the Moon's ephemeris position on the predicted times for the total solar eclipse of January 3, 1908. Mr. Tucker found that the Moon was more than 0.4 of a second east of its published position. This discrepancy would cause the eclipse to occur about twenty seconds of time earlier than predicted. The optical system of the Crossley reflector consisted exclu- sively of the 36j^-inch silver-on -glass mirror, which has a ratio of aperture to focal length of i : 5.8. This ratio is not suitable for the collimator of a spectrograph, and, likewise, the scale of stellar photographs is too small to admit of the very accurate observations required in parallax detenni nations. Quite extensive investigations by Dr. Perrtne and Dr. Albrecht established clearly the desirability of reducing the magnitudes of unavoidable errors by increasing the equivalent focal length. To this end Mr. F. G. Pease, expert optician to The Scientific Shop, in Giicago. spent four weeks on Mt k 188 Publications of the Hamilton in the summer of 1907, figuring a 9^-inch hyper- bolotdal mirror for the Crossley reflector, in order to convert the telescope into the Cassegrain form. A third mirror, with flat surface, is mounted diagonally with reference to the incident light, immediately in front of the parabolic mirror, in order to direct the beam through the side of the tele scope -tube near its lower end. The equivalent focal length has been increased by the combination to about seventy feet Professor Perrine, who dcsigTied the necessary mechanical additions. and assisted Mr. Pease in the tests, is hoping promptly to utilize the telescope, thus modified, in the development of stellar-parallax methods, and Mr. Campbell is planning for spectrographic work on certain especially interesting types of stars in the near future. The most extensive investigation under way is that of deter- mining the radial velocities of the brighter stars by means of the Mills spectrograph attached to the 36-inch refractor, in accordance with a programme entered upon by Mr. Campbell in 1896. This programme hopes to include all the stars whose photographic magnitudes are equal to or brighter than 6,0, lying north of — 25° declination, with the addition of essentially all of the stars brighter than the fifth magnitude between — 25° and —30° declination. The number of stars on the list is approximately 750. but a certain number of these are not amenable to accurate observation, for the reason that their spectra do not contain sharply defined lines. The number of spectrograms secured with the 3-prism Mills instrument in 1907 was approximately 500. The total number of spectro- grams obtained up to January I, igo8, was 5,086. The number is not increasing so rapidly in recent years as fonnerly, because the greater part of our attention is now given to fainter stars requiring longer exposures. It is interesting to note that we have found it possible to use wider slits and, at the same lime, obtain spectra of sufficient purity to permit accurate measure- ment. In this way we are able, under average conditions of seeing, to obtain good spectra of stars of 6.0 phot<^raphic magnitude in from two hours to two and a half hours. Of the 500 plates exposed in 1907, practically all have been measured and reduced approximately, and fifty definitively. The observing in this programme was carried on by Messrs. 'onomical Society of the Pacific. 189 Campbell, Wright, Moore, and Albrecht. Since November 1st, Mr. H. C. Plummer, Fellow, has also observed regfularly. Occasional assistance was rendered by Carnegie Assistant K. Burns, by Fellows J. C. Duncan and E. A. Path, and by visiting astronomers Dr. C. A. Chant and Dr. A. B. Turner. During the year eleven spectroscopic binaries were discov- ered in the course of the regular observing programme — one by Mr. Campbell, one by Mr. Plummeb, and nine by Mr. Moore. Dr. MooBE is making a new investigation of the orbit of the variable binary-star 8 Cepkei. forty-one 3-prism spectrograms having been secured in 1907 for this purpose. Two hundred and fifty definitive measures of 3-prism spec- trograms, made by Carnegie Assistant Newkirk up to the date of his departure in September, have been reduced by Miss Leah Allen. Carnegie Assistant. The measures and reductions of all spectra taken with the Mills spectrograph between August, 1907, and July, 1903. were completed by Carnegie Assistant Burns in July, 1907, as the result of his three years' work. Mr. Buhns's extensive spcc- trographic investigation of the rotation of Venus, while not yielding positive evidence as to the rotation period of that planet, was valuable in making dear the elements of the problem and in indicating the desirable features of apparatus and methods for obtaining a satisfactory solution. Spectrographic observations of Polaris obtained in the past two years show that the velocity of the bright component in the line of sight is slowly approaching that observed by Mr. Campbell in 1896. The long period of this interesting triple star cannot now be defined, but it is probably between twelve and twenty -five years. Dr. A. B. Turner, of the College of the City of New York, completed his investigation of the orbit of the spectroscopic binary w Draconts, which he carried on during the summer vacations of 1906 and 1907. Dr. Albrecht's paper on "A Spectroscopic Study of the Fourth Class \'ariable Stars, Y Ophiuchi and T Vulpecula," completed in 1907, brought out the fact that, in the h-Cephei class of variables, a relation apparently exists which promises to be extremely significant in determining why these stars Publications of ike vary. He found, in the ten stars of this class thus far inves- tigated, that the maximum of brilliancy occurred at or very near the time when the bright component of each of these binary systems was moving toward the observer. No excep- tion to this nile has been noted. Inasmuch as the ten observed stars arc distributed through a considerable area of the sky, it is surprising to find that the time of greatest brightness is apparently dependent upon the observer's position in space. It may easily transpire that this is one of the most significant discoveries concerning variable stars made in recent years. The work of the D. O. Mills Expedition to the southern hemisphere, internipted in 1906 while numerous improvements in and additions to the apparatus were made, and more or less by the great earthquake of August, was prosecuted vigorously by Astronomer Curtis and Assistant Paddock throughout the year 1907. A large number of stellar spectrograms were secured with the 3-prism, 2-prism, and i-prism instruments. All of these were measured and reduced provisionally, and many of them definitively. The orbits of several interesting spectroscopic binary stars were investigated and published. The diurnal range of focal length, caused by rapid changes of temperature, formerly so troublesome, has been eliminated by Dr. Curtis through the use of the refrigerating apparatus recently described in these Publications. The measurement and reduction of the 800 spectrograms obtained during the original two-year period of observation by Professor Wright and Assistant Palmer were completed on Mt. Hamilton about the middle of 1907 by Messrs. Wright and Aluhecht. Both have made extensive studies of systems of normal wave-lengths to be used as a basis for applying the final corrections to the sontliem hemisphere results. Dr, Alfrecht continued during the year, as time was avail- able, his study of the effective wave-lengths of spectrum lines as dependent upon spectrum type. Dr. AiTKEN has continued the double-star survey of the northern sky. according to the systematic plans described in fonner reports, During the year 1907 he examined about 8,500 stars, down to the 9.0 magnitude inclusive, with the 12-inch and 36-inch refractors, and 250 of these Stars were found to be double, all the pairs having distances less than five seconds. This number is smaller than that reported in 1906, partly because of unusually bad observing conditions in the first half of the year and partly because of absence on the eclipse expedition. These discoveries include a number of pairs likely to prove of more than ordinary interest. We may mention the very close and bright pairs k Ursa Majoris (4.5 magnitude) and v' Bootis (5.0 magnitude). It is expected that this survey, as carried on at Ml. Hamilton, will extend to — 22° declination. Fully eighty-five per cent of the survey has been completed, and, given ordinary observing conditions, this section of the work should be finished in the summer of igio. Prior to January, 1908, more Hian 3,000 close doubles had been discovered, as one result of the survey — 1.300 + by Professor Hl'ssev and 1,700 by Professor Aitken. It is scarcely necessary to say that the great value of this notable survey lies not in these discoveries themselves, but in the enormously increased opportunity which the discoveries will afford in the future study of double stars in particular and of the structure of the sidereal universe in general. Holding the requirements of this study in mind, the systematic qualities of the search are rigidly maintained, and at least two satis- factory micrometer measures of each pair are secured, as promptly as practicable, before announcing the discovery. It is hoped, for example, that future computers of their orbits will have the great advantage of an acairate discovery -posit ion in every case. About one hundred of the more important and difficult of the well-known double stars are kept under observation, meas- ures being made as often as they are needed to improve our knowledge of the orbital motion. To refer to only one pair: Dr. Aitken's measures of the binary 13 Celt, discovered by Hough in 1886, have enabled him to establish that the revolu- tion period of this system is only 7.4 years ; next to that of 8 Equulli, the shortest period known. Micrometer observations of the satellites of Uranus and of the inner satellites of Saturn were continued by Dr. Aitken with the 36-inch refractor. Eclipses of Saturn's satellites were observed on six nights, and close attention was given to the phenomena presented by Saturn's rings, whose plane passed through tile Earth twice and through the Sun once during 192 Publications of the the year. The causes of the curious bright knots, or con- densations, observed in the rings, here and elsewhere, are undergoing discussion in several journals, and our knowledge of the structure of the rings promises to be increased. Micrometer observations of comet positions have been obtained as follows: — Comet a 1907, 2 nights, Aitken Comet 01907, 4 « Fath Comet b 1907, 6 <( Aitken Comet C1907, I (t Aitken Comet (/1907, 4 « Aitken Comet ^1907, 12 « Duncan Comet IV 1905, S « Aitken Comet e 1007, 7 t( Duncan Comet 1905 IV, discovered by Kopff in March, 1906, and later found on photographic plates taken at Heidelberg in January, 1905, was under observation for a longer consecutive time than any previous comet. Micrometer positions of asteroids have been obtained as below : — Nemesis (128), 2 nij^^hts, Aitken. Mr. Fatii, Fellow, began an extensive study of the zodiacal light, with special reference to polarization effects and the character of its spectrum. One spectrogram exposed by Mr. Fath on several successive nights, and another exposed for Mr. Fath's use by Mr. Duxcax, recorded the spectrum in good strength. The study will be renewed on Mr. Fath's return in the summer of 1908. Interpretation of the observations will be deferred until more data are available. Observations of Jupiter s satellites VI and VII, with the Crossley reflector, were secured by Messrs. Perrine and AumECHT. The ap]:)lication of electric ])ower to moving the Crossley dome and to winding the clock, in combination with the splendid clock-driving, has rendered unnecessary the services of an assistant to the Crosslev observer. Good progress was made in the preparation of heliogravure plates of Professor Kkefjir's nebular photographs, with refer- ence to their ])ublication in volume form. To secure satisfac- Astronomical Society of the Pacific. '93 tory reproductions by mechanical processes has been a long struggle, so great are the difficulties encountered : but it is confidently expected that the volume will be ready in 1908. This arduous task has been in Dr. PERHiNE's charge. Comet d 1907, discovered by Daniel, was the brightest comet that had been in good observing position since 1893. Advantage was taken of this fact to secure a splendid series of photographs. Exposures were made by Mr. Dun'CAN on thirty-six nights, from July 10th to September 12th, seventy- one negatives in all. These photographs, forming as nearly continuous a series as the weather and the moonlight permitted, exhibit admirably the progressive changes occurring in the head and tail as perihelion was approached, and likewise sev- eral interesting phenomena of an irregular character. In general, the changes were very rapid. It is probable that the tails of one night were entirely replaced by tails composed of new matter on the following night. A noteworthy fact was that whenever any of the streamers appeared as curves, their convex sides were turned toward the other streamers, suggest- ing strongly that the particles in the tails repel each other. Only the negatives of July loth and nth recorded well-defined condensations in the tails. Fortunately, Professor Barnard obtained a photograph of the comet on July tith, at the Ycrkes Observatory, a copy of which he kindly supplied to us. In the 2" 25"' elapsing between the taking of the Yerkes and Lick plates, the displacement of the prominent condensation was very marked. Although the nucleus of the comet was ap- proaching the Sun, the condensation receded from the Sun. Mr. Duncan found its velocity away from the nucleus to be 44""" per second, and from the Sun 15""" per second. Several less definite structures were observed on later plates. Two exposures having been made here on the same night, when- ever possible, Mr. Duncan was successful in detecting outward motion in several cases; and the velocity of recession was always the greater for greater distances from the nucleus. This is as it should be, assuming their motion to be due prin- cipally to a continuously acting repulsive force emanating from the nucleus, or from the Sun, or from both. Polarization observations of the comet, made by Messrs. Duncan and CAMPBEi.r., seemed to show that the proportion 194 Fublicattons of the of polarized light decreased rather rapidly as the comet 1 proadied the Sun; indicating that its light at first consistec largely of diffused sunlight and later mostly of light inherent to the comet or of sunlight reflected to us by large partides forming the nucleus. The spectrum of the comet was studied by Mr. Campbell. It was at first almost free from the bright bands of carbon and cyanogen, but in late August and early September these became very prominent. The best spectrograms showed the spectrum of the nucleus to be a close approximation to the solar spectrum (reflected sunlight, apparently not polarized strongly), and the spectrum of the coma to consist largely of a great number of bright lines. The photography of comets, applied with great success, first by Professor Barnahd at the Lick Observatory and subse- quently by observers at various stations, has made clear the fact, undoubtedly very significant, that the tails of these bodies undergo exceedingly rapid changes. It is not too much to hope that a thorough study of these internal changes will shed strong light on the origin, composition, and physical conditions of cometary bodies. Bright comets, naturally, keep to the region of the sky immediately surrounding the Sun, and for this reason it is seldom practicable for the same observer to secure more than one good photograph per night. In these days of astronomical co-operation, we cannot find a subject more worthy of co-ordinated effort on the part of different observatories than that of comet photography. It is high time that such an organization be perfected, to care suitably for the bright comets of the future. The interests of observers pro- vided with telescopes suitable for photographic comets, both in this country and abroad, should be enlisted and organized, so that, as a comet is successively in position for these ob- servers, covering a wide range of terrestrial longitudes, photographic records will be obtained suitable for subsequent comparison. The general plans for the observatory were made in the late 70's and executed in the early 8o's. at which time astronomers did not realize the important part that photography was des- tined to play in their researches. Consequently, when the institution was opened, on June i, 1888, it did not poss Astronomical Society of the Pacific. 195 suitable apparatus and rooms for taking celestial photographs and for their measurement and study. Director Holden pro- ceeded energetically and wisely to transform the equipment to meet photographic requirements. - Fortunately, gifts from out- side sources, and such small sums as could be spared from the maintenance funds, provided for photographic telescopes, spec* trographs, and measuring microscopes. Space suitable for the storage and study of photographs has been a pressing need, and the successive annual reports of Directors Holden, Keeler, and Campbell have drawn attention to this need. The last two legislatures appropriated small sums to begin such a building. With these funds a section of the building was erected in the late fall of 1907, of reinforced concrete. It includes three storage vaults on the first floor, and an enlarging room fifty feet long on the second floor: one third the space of the finished building as planned, erected at one half the total cost. It is hoped that the next Legislature will provide for its completion, in 1909. The installation of the electric plant, begun under great and unnatural difficulties immediately following the earthquake and fire of April, 1906, was completed in June. 1907. A twenty horse-power gasoline engine, using distillate, is directly con- nected to the dynamo, which charges a storage battery of 128 cells, each having a capacity of 200 ampere hours. The battery serves as a reservoir of power, to be drawn upon as required. Apart from current for producing comparison spectra, main- taining the spectrographs at constant temperatures, lighting micrometers, and for other purely scientific work, it is drawn upon to turn the domes of the 36-inch refractor and the Crossley reflector, to wind their clocks automatically, to run the machinery in the instrument-making and carpenter shops, to operate two pumps in the water systems, to saw fuel for the community, and to illuminate all the buildings. The entire plant is operating satisfactorily, and is a great addition to the resources of the observatory. In particular, the use of motors in winding clocks f automatically 1 and turning domes has perceptibly increased the observing efficiency, A considerable list of minor scientific results and additions to equipment should, for completeness, be mentioned, but space is lacking. W. W. CAMPBE.t.L, DVrecloT. GENERAL NOTES. Planetary Nebula unth Variable Nucleus. — Professor Barnard some years ago suspected a variation of the bright- ness of the nucleus of the planetary nebula N. G. C. 7662. In Monthly Notices R. A. S., April, 1908, he g^ves the observa- tional evidence, mostly secured by himself in the last ten years with the 40-inch telescope, from which he finds a variation of three or four magnitudes and a period of about twenty-eight days. The nucleus is faint — near the limit of the great re- fractor—except for a few days of the four weeks, when it appears like a bright yellowish star of about the twelfth mag- nitude. Professor Barnard finds confirmation of the vari- ability from his own photographs in 1899 and 1900, and from early observations with the Rosse telescope and Lassell's four-foot reflector. Professor Turner (loc, cit.) finds that the data are fairly well satisfied by the period 27^ days. Professor Kapteyn has been elected an honorary member of the Royal Irish Academy. The 7-inch Reinfelder-and-Hertel refractor of the Manora Observatory, Istria, Austria, is being offered for sale. Unusually good performance is reported for this instrument. There seems little doubt that the faint object discovered by Mr. P. Melotte on Greenwich Observatory photographs in the region of Jupiter is a new satellite (VIII), with retrograde motion, and distance from Jupiter of about 20,000,000 miles. — The Observatory, May, 1908. Mr. J. EwEN, of Edinburgh, has constructed a highly reflect- ing model of Saturn and his rings, which, when illuminated by a strong light in the plane of the rings, shows two tiny luminous knots on either side of the ball. Spinning the model causes the knots to shift inward, the shift increasing with the speed of rotation. — The Observatory, April, 1908. Publications of the Aitronomtcal Society, Effc. 197 M. P. ViNCART, of Antwerp, can, with the naked eye, count thirteen of the Pleiades stars, and see Jupiter's third satellite at opposition. — Journal B. A. A., from Nature of March 19. igo8. The Paris Academy of Sciences has appointed a committee to consider the feasibility of sending a signal at midnight each night from the wireless telegraph station on Eiffel Tower, to aid navigators at sea in determining their longitude, — Science. The Rnmford Committee of the American Academy has made a grant of one hundred dollars to Professor Joel Stebbins, of the University of Illinois, for his investigation on the use of selenium in photometry.— 5'ciV'Jcc. Notes from "Science."— The directorship of the Toulouse Observatory, vacant by the appointment of M. Baillaud to the National Observatory, has been filled by the election of M. E. COSSEHAT. M. H. Deslandhes, who since 1897 has been assistant director of the observatory at Meudon, has been appointed director to succeed the late Dr. Janssen. Professor H. Poincabe, professor of astronomy in the Paris Ecole Poly technique, has retired with the title of honorary professor. M. Mauhice Hamv, of the Paris Observatory, succeeds the late Dr. Janssen as a member of the Paris Academy of Sciences. Director Eiiwm B. Frost, of the Yerkes Observatory, Uni- versity of Chicago, has been elected a member of the National Academy of Science, and Dr. Hugo Ritter von Sf.eliger, professor of astronomy in the University of Munich, has been elected a foreign associate by the same institution. The Allegheny Observaiory.^AiteT a period of construc- tion extending over a number of years the .'\llegheny Observa- tory, in its new location, is again making valuable contribution to the science of astronomy. Five parts of Volume I, Publico- 198 Publications of the Astronomical Society, &c. tions of the Allegheny Observatory, have recently been issued under the following titles : — No. I. "On the Distortion of Photographic Films." No. 2. "A Simple Method for Reducing Spectrograms." No. 3. "The Orbit of a Andromedce." No. 4. "The Radial Velocity of c Ursce Majoris," No. 5. "The Orbit of Algol from Observations made in 1906 and 1907." The authors of these investigations are Dr. Frank ScHLESiNGER (Director), Dr. R. H. Curtiss, and Mr. R. H. Baker. Volume I, No. i (April, 1908), of the Astronomical Herald, published by the Astronomical Society of Japan, was received recently. The title and table of contents are printed in English, but all of the text is in Oriental characters. NEW PUBLICATIONS. Abbot, C. G., and F. E. Fowle. Annals of the Astrophysical Observatory of the Smithsonian Institution. Vol. II. Washington. 1908. Folio. 245 pp. Paper. Abetti, Giorgio. Ein neuer Hippscher Chronograph mit festen Spitzen. Mitteilungen der Grossh. Sternwarte zu Heidelberg, XII. Karlsruhe. 1908. 8vo. 15 pp. Paper. American Ephemeris and Nautical Almanac for the year 1911. Washington. 1907. 4to. 595 pp. Qoth. Annales de TObservatoire d'Astronomie Physique de Paris. Tome Troisieme. Second fascicule. Paris. 1907. 4to. Ill pp. Paper. Annuaire pour Tan 1908, public par le Bureau des Longitudes. Paris. i6mo. vi + 760 + A 72 + B 48 + C 12 + D 18 + E 7 + F 41 pp. Paper. Gauthier-Villars. Price, i fr. 50 c. Arrhenius, Svante. Worlds in the making. Harper, and Brothers, New York. 1908. 8vo. Cloth. $1.60 net. Belopolsky, a. Untersuchung der Radialgeschwindigkeit des veranderlichen Sterns Algol (p Persei) in den Jahren 1905-1907. Mitteilungen der Nikolai-Hauptstemwarte zu Pulkowo. Band II, No. 22. Folio. 34 pp. Paper. Berichtigimgen zum Catalog der Astronomischen Gesellschaft. Erste Abtheilung. Cataloge fiir 1875. Leipzig. 4to. 33 pp. Paper. BoHM, Josef Georg. Die Kunst-Uhren auf der k. k. Stern- warte zu Prag. Auf offentliche Kosten herausgegeben von Dr. Ladislaus Weinek. Prag. 1908. 4to. xi -}- 48 p. Mit 21 Tafeln in Lichtdruck. Boards. Catalogo Astrofotografico 1900.0 Zona di Catania fra le De- clinazioni + 46° e -}- 55°. Vol. V, Parte I*. Declinazione + 50° a + 52°. Ascensione Retta o** a 3**. Catania. 1907. 4to. xxxvi -}- 143 pp. Paper. DooLiTTLE, Eric. Catalogue and re-measurement of the 648 double stars discovered by Professor G. W. Hough. Pub- lications of the University of Pennsylvania. Astronomical series. Vol. Ill, Part III. Philadelphia, 1907. Folio. 176 pp. Paper. 200 Publications of the Hale, George E. The study of stellar evolution: A popular account of some modem methods of astrophysical re- search. Chicago. 1908. 8vo. 250 pp. 104 plates. Qoth. $4.00 net. Hartwig, Ernst. Ueber den Antalgolstem RW Draconis. Sonderabdruck aus dem XIX und XX Bericht der Naturforschenden Gesellschaft. Bamberg. 8vo. 32 pp. Paper. Hartwig, Ernst. Ephemeriden varanderlicher Sterne fiir 1908. Leipzig. 1908. 8vo. 78 pp. Paper. Kayser, H. Handbuch der Spectroscopic. Vierter Band. Leipzig. 1908. 8vo. xix + 1248 pp. Mit I Tafel und 137 Figuren. Paper. Kapteyn, J. C. On the number of stars of determined magni- tude and determined galactic latitude. Publications of the Astronomical Laboratory at Groningen, No. 18. Gronin- gen. 1908. 8vo. 54 pp. Paper. Kustner, F. Katalog von 10663 Stemen. Veroffentlich- ungen der Koniglichen Stemwarte zu Bonn, No. 10. Bonn. 1908. Folio. 333 pp. Paper. Nautical Almanac for 191 1, The. Edinburgh. 1907. 8vo. xiii -f- 614 + 44 PP- Paper. Price, 2s. 6d. Observations faites au cercle meridien en 1906, par M. M. VeRSCHAFFEL, LAHOrRCADE, L. SOUGARRET, SONEGUIETA, Goulart, Beigbeder, Dupouy, et Miles. D. Sougarret et Lie Sougarret. Observatoirc d'Abbadia. Tome VL Hendayc (R. P.). 1907. Folio, vi + 426 pp. Paper. Pickering, Edward C. Sixty-second annual report of the director of the Astronomical Observatory of Harvard College for the year ending September 30, 1907. Cam- bridge, Mass. 1908. Svo. II pp. Paper. Przyhyllok, E. Das Profil der Raudpartien des Mondes. Mitteilungen der Grossh. Sternwarte zu Heidelberg, XL Karlsruhe. 1908. Svo. 31 pp. Paper. Rees, John K., Harold Jacoby, and Herman S. Davis. The variation of latitude and constant of aberration. Part H. Contributions from the Observatory of Columbia Univer- sity, New York, No. 9. New York. 1906. Folio. 231 pp. Paper. Astronomical Society of the Pacific. 201 Repsold, Joh. a. Zur Geschichte der Astronomischen Mes- swerkzeuge von Purbach bis Reichenbach, 1450 bis 1830. Leipzig. 1908. Folio, viii +132 pp. Mit 171 Abbil- dungen. Qoth. ScHEiNER, Julius. Populare Astrophysik. Leipzig und Ber- lin. 1908. 8vo. iv + 718 pp. Mit 30 Tafeln und 210 Figuren in Text. Cloth. Turner, Herbert Hall. Astrographic catalogue 1900.0. Ox- ford section, declination -}- 24° to -}- 32°. Vol. Ill, Meas- ures of rectangular co-ordinates and diameters of 62713 star images on plates with centres in dec. -}- 29°. Edin- burgh. 1907. Folio. XXV + 224 pp. Paper. Price, 15s. Vol. IV, Measures of rectangular co-ordinates and diam- eters of 65808 star images on plates with centres in dec. -}- 28°. Edinburgh. 1908. Folio, xxvi + 233 pp. Paper. Price, 15s. 202 Publications of the .Astronomical Society, ..fr«J|^^ OFFICERS OF THK SOCIKTV. Mr. ClIA«lJll BU«C»HAl.TB« Mr. W. W. Caijmeh. F(*« yici-l Ut. G. E. Hali Stcani yietprttiditt Mr. F, Maui Third Vir-Priadnt Mr. R. T. C»AWfo«o (StudenW OtMcmiarj, BerkelcT) Srertlarj Us. R. G. AiiKiH (Monnt HanilWn. C>l.) Sterttary Mr. J. D. GULOWAI TriaimrtT Beard of Dwtctart — AnKXH, BuaciBALiEB. CAHrtiu., Ciawtcui, Cipctu. CuauiKc, Galldwat. Hale, Mansi. RiCHA>utON, Town let. Fiitanci ConimilJH — Meiin. CusBiHC, Ciocxu. Aiteik. Library Cemmiltet—Mrtict, Cuwnjuii, ToH'KLEY. ElMAlBON. ^^H t VIII of the Br-L«n. Ficific, Slude of ibe PHblict Krvatorr, Berkeler. each member of Ibe Society sball receii ^r the year in which be waa elected to If there bave been (unfunuiuitely) i Stud CD ts' Ot The Com.„ are printed in the Publi Berkeiej, Cal. iom i> dc ited first of publication. aulEors wboae ri enl la the members, wbo can tbcu Iplcte TOlnmei for past years will the SecreUriM, Any nan-rciidait lOks from Ibe Society'a library by return Ibe book >ad the cud. y that the order in which paperi ly by mnvcDience. In ■ (ECDenl earliest accepted for publiCAtiDn. r of [he PublicoiiBm ihould be in 20tb of the month precedint dale e United Sut«. Tbe immoniciiicd to either of the Sec~ nge» in addreiaM. The Secreiuj ociety sniublc lUiionery. itainped iltows; a blocE of letter paper, 40 These prices P^'ULIC LISKARY TILDEN FOUNOA7lO>*e. Fig- I.— Hydrogen Floccdu, Photoosaphed with the Wa Line 1908, May I, 41" 48" P. M. Scale; -Sun's Diainelcr = o 2 Meier Fia. l.^HvT,Bn,:w PUBLICATIONS Astronomical Society of the Pacific. Vol. XX.. S*H FiAXCiMO, CaufoKhia, August 10, 1908. No. 121 SUL.AR VORTICES.' The problem uf inlerpreliiig the complex solar phenomena recorded by die spectroheliograph ha& occupied my atteiuion since the first work with this instrument in 1892. The meas- nremenl of the daily motions in longitude of the calcium flocciih has led to several new determinations of the solar rotation,^ and their areas, measured by a photometric method, are being used as an index to the solar activity. Various investigations on their forms at different levels,* their distri- bution in latitude and longitude, etc., have also been carried out. But the failure of the calcium Hocculi to indicate the existence of definite currents in the solar atmosphere has been a disappointment. The hydrogen flocculi, though occupying the same general regions on the Sun's disk, are distinguished from those of calcium by several striking peculiarities. In the first place, most of them are dark, while the corresponding calcium (Hj) flocculi are bright. Secondly, as I have recently shown,* they seem to obey a different law of rotation, in which the equa- torial acceleration (better, tlie polar retardation) shared by the spots, faculaf and calciinn flocculi, does not apjjea'r. .-\ third peculiarity, briefly mentioned in previous papers, is • CBHIribulinni from llu Meanl I ' KiLK snil Fox, " Tbe Raialioo ( ihe CbIciuui Flocculi." firnigie Inatllolloi 07- Kali, Cnntribuiiant fram Ihi MmdI e. in which I had the assistance of Mr. Adams, indicated that bright flocculi are more numerous and extensive when pliotographed with Ha than when HB is used. I then tried Ha with the five-foot spectroheliograph of the Snow telescope, and imme- diately obtained excellent results. The images were stronger and of much better contrast than those given by Hi. More- over, the curved and radial structure surrounding sun-spots was so striking as to lead to the hope that important advances might be expected to follow from the systematic use of the Ha line. On account of the difference in curvature of Ha and Hi, these preliminary photographs, made with H6 slits, showed only a very narrow zone of the solar image. A new pair of slits, of suitable curvature for Ha. was accordingly made for the five-foot spectroheliograph, and as soon as these were ready I completed the adjustments of the instrument, with Mr. Ellerman's assistance, and made comparative photo- [the t-.^^:r^^HK! PUBLIC LlbAAr.X A»TOR, LSNOX »N» TILOEN FOUNDATION*. ^^r IT ^^^ ^ Figs. 2 a 1 FlO. 1.— PEOMINENCES At EASTEkN LtUB OF THE SUS 908, May it, t^ 38W A. 11. Scale; Sun's Diam«er-o,3 Mtt D J— PdOUlNENCES PhOTU^IRAI-HED WITH HS (FlO, j) AND I igoS. Aprii 3. Scale: Sun's niameler = o.,i M^ltr ;]SD b« inipoii a[>t la r d darV hydrogen line. lAtttepkytiial Jeurii \<,\. XIV, V. 1,3) will »pp!y 10 .ol ' ■*■«-"■■ « [THE N-VV v.^HK PUBLIC Llrf^.-.KY ^,T»". LENOX »«• TILDEN FOUNDATIONS 4 The Sun, Showimi the Hvdkqcen (//a) Flocctli LA i n THt NtW YOKK PUBLIC LIBKAHY n 1 r ^ THE NEW YORK PUBUC UBRARY Airan. lemox •»■ TILDEN rOUNDATKINa Direct Photoobaph of the Sos 1908, April 30, 6*' 35™ A. u. Astronomical Society of the Pacific. 207 rapidly changing phenomena. This would mean almost unin- terrupted exposure of the mirrors to sunlight, and such serious distortion that the astigmatism would ruin the photographs. At this point experience with the tower telescope came in to good advantage. The very thick mirrors used with this instrument are not ajiprcciably distorted in sunlight:' hence it seemed prnbahle that by reducing the aperture of the Snow telescope mirrors the increase in their relative thickness would relieve the difficulty. I therefore commenced a series of experiments with different apertures, and finally adopted a 15-inch (38™) diaphragm for the ccelostat in place of the full aperture of thirty inches (/fi™). With this the focal length does not ordinarily change perceptibly during a single exposure. When the mirrors are in sunlight, with very brief interruptions, during a period of an honr. the focal length gradually increases, bm tlie effect of astigmatism is hardly appreciable. In the work with f/8, the hydrogen floccuU could not he (ihotographeil with sufficient contrast unless the very slow "Process" plates (also used for H, and H,) were employed. These plates gave excellent results with Ha. but could not be used after the aperture had been reduced to fifteen inches without undue increase of exposure time; hence it was neces- sary to substitute for them Seed's "Gilt Edge" plates, which fortunately serve very well with this line. The first experi- ments with !la were made about the middle of March. On March 28th the new slits were in place, and the fir^;! photo- , graphs of the entire disk were obtained. During April the weather was not very favorable, but nn April 29th and 30th Mr. Ellekman, then in 'charge of the routine work with the five-fixit spec troll ehograph, secured some remarkably fiiie negatives. The one taken on April 30th is reproduced in Plate in. Apart from the whirls, which may be seen to better advantage in Plate I\", this photograph shows in projec- tion an enormous prominence in the southern hemisphere. This also ap|>ears. though much less satisfactorily, on the Ha photograph of May ist. and may be traced on the Hi photo- graph of the same date I Plate I). Publications of the But. in spile of its great intensity and length, this promi- nence is of minor interest in comparison with the structnre shown in Plate IV. This is so definite in form and so unmis- takable in character as to satisfy the hopes aroused by the earlier photographs. It seems evident, on mere inspection of these photographs, that sun-spots are centers of attraction, drawing toward them the hydrogen of the solar atmosphere. Moreover, the clearly defined whirls point to the existence of cyclonic storms or vortices. The most striking of these storms occupies an enormous area in the southern hemisphere, extending from the equator to about 35° south latitude and about 50° in length.' Xear the center of this region, partly covered by clouds of bright hydrogen, lies the small spot-group shown (from a direct photograph) in Plate V. The corresponding H^, photograph reveals a large calcium flocculus over the spot-group ( Plate VI). but this, though of great size, appears to differ in no essential particular from ordinary calcium floccuti, and gives no evidence of gyratory motion. A good Ha photograph was obtained on April 29th, but it was badly stained in the sensitizing process, and many of the flocculi are hidden by streaks on the negative. Fortunately, the greater part of the targe storm area is fairly well shown, so that comparisons with the afternoon photograph of April 30th may be made in the stereocomparator (using the monoc- ular attachment). On account of the changes in form of the flocculi during this interval, the identification of objects suit- able for measurement is very difficult and uncertain. Three independent determinations of the positions of certain flocculi on the two plates have been made by Miss Ware. The objects identified on both dates were marked by small dots of ink on the glass side of the negative, and their latitude and longitude measured with the heliomicrometer. When reduced to the same epoch (using for the value of the daily angular motion $ — 14°. 5, derived from the measurement of 828 points on thirty-five lH plates), the plotted results seem to show the existence of a gyratory motion, in a direction opposite to that of the hands of a watch (north, east, south, west). Although »ly lot Astronomical Society of the Pacific. 2& most of the points in a given region appear to move together, there are a sufficient number of apparently opposed motions to weaken seriously the value of the evidence. Unfortunately, an Ha plate taken on the morning of April 30th is not sharp enough to assist in the identifications. Further discussion of these plates is therefore postponed until additional data become available. On account of the complex character of such storms, a large number of photographs, taken at sufficiently short intervals to permit the flocculi to be identified with certainty, will be required to give satisfactory results. As our recent plates show that these storms are of common occur- rence, and probably accompany every group containing several spots, there should be no difficulty in obtaining suitable photographs. In the present paper I wish to illustrate the phenomena recorded with the aid of Ha in the neighborhood of a spot which reached the east limb of the Sun at S"" 16"° a.m. on May 26th, 1908. A photograph of this spot, made by myself with Ha on May 2yth, at 4" 26"" p.m., Pacific Standard Time, is re- produced in Fig. I, Plate VII. The whir! structure, which is clearly shown by this photograph, is also very distinct, though of somewhat different form, on the photograph of May 28th. It is interesting to inquire as to the probable level of the region in which this whirl occurred, and the height of the long dark flocculus south of the spot. For this purpose we may examine photographs of the chromosphere and prominences at the limb, taken on May 25th, 26th, and 27th. In the first of these, made on May 25th, at 9'' 18" a.m. (No. 4142), a long, narrow prominence, extending toward the north, rises from the limb at position-angle 92°, a point about one degree north of where the spot would be. It makes an angle of about 12° with the limb, and fades out at the upper end, its length being approxi- mately 90" (geocentric). There are other small filamentary prominences in the region extending about 7° north of the spot, and smaller elevations in the chromosphere to the south. At posit ion -angle 98° a bright prominence rises to a height of about 20", and then slopes to the chromospheric level at position -angle 107°. Near its southern end is an independent filamentary prominence about 55" high. On May 26th. at 6* 38" A.M. (No. 4144), the prominences shown in Fig. i, k Publiralions i Plate II. were photographeil at the east limb. The lowest point in the chromosphere on this photograph corresponds to the position fP. A. 93°) where the spot crossed the limb about two hours later. It will be seen that these prominences, which extend from position -angle 82" to 106'. cover much of the region in which the whirl structure of Plate VU appears The prominence south of the spot is very bright and its highest point reaches an elevation of about 35". On May 27th, ax 5" 22™ P.M. (No. 4152). a prominence about 25" high extends from position-angle 105° to ioq°. This is doubtless the eastern extremity of the strong flocculus in Plate \'\\, which mav there be seen curving toward the spot. We may now pass in rapid survey the more important photo- graphs of the disk. On May 28th. at 6'' 58" .a.m. CNo. 4157). the spot is near the east limb and the whirls are well shown To the east of the S[x>t is a long, narrow line of bright hydro- gen. On May 2yth. at 6" 24" .\.m. (No. 4171), the whiri-^ are very distinct and differ in many respects from those sliown on May 28th. Eniptive regions of bright hydrogen are seen southeast and west of the spot. The eastern end of the long, dark flocculus is changing in form, and bridges are appearing over the spot. Negative No. 4175. taken i" k)"" later, seems to show distinct changes in the whirls, though they are not measurabk. On May 29th. at 4" 26" p.m. (No. 417ft), the whirls resemble those shown in negative No. 4175. but exhibit some marked changes. An eniption. which appears on the fonlier plate southeast of the spot, continues, bnt is changed in form and less brilliant than before. A strong eruption, of peculiar form, appears southwest of the spot, and bright hydro- gen to the northeast. Strong dark flocculi have also developed at many point.s around the .spot. The eastern end of the long, dark flocculus is still changing, and a projection appears west of its center (see Plate VIM. A negative taken on the same day, at 5'' 13" p.m. (No. 417S). shows further changes both in the bright and dark structure, especially in the region south- west of the spot, A fork has developed in the western end of the long, dark flocculus, and a small but very dark flocculus appears just west of the spot. Another photograph (No. 417QI. the first exposure of which was made at ^ 26" p.m.. shows a bright eruption west of the spot, where the small. Astronomical Society of the Pacific. 211 dark lloccLiUis appears on No. 4178. The eruption nmlerwent considerable change of form while the five exposures on this p!ate. separated by intervals of a few minutes, were bein^ made. At 6* 04" p.m. negative No. 4181 shows that the erup- tion had .nibsided, and brings out other definite changes in structure near the spot. The small, dark flocculus has dis- appeared. On May 31st, at 8" og"' a.m. (No. 4188). the fork at the western extremity of the long, dark flocculus has par- tially closed. No eruptions api^ear west of the spot, but there are bright ones to the southeast. Other important changes are evident, and the two bridges across the spot are conspic- uous. On June ist, at 6" 30™ a.m. (No. 4189). the fork at the western end of the long, dark flocculus appears more nearly as it did in negative No. 4181, and the two bridges over the spot are very marked. A negative taken fifteen minntes later (No. 4190), shows distinct changes, especially in the region south and southeast of the spot. At 5'' 08" p.m. of the same day negative No. 4193 shows a more distinct whirl near the spot, and the long, dark flocculus api>ears to be grow- ing shorter at its eastern end. On June 2d, at 6" 10" a.m. (No. 41961, the whirling .stnicture is very marked and more nearly symmetrical about the snot, which is divided into two parts (Fig. 3. Plate \'IIV At 7" 27"" \.m, (No. 41Q8), the whirl is also very marked and somewhat changed in form. I'p to this time the changes, while in many cases rapid, were not especially violent. On June ^d, in an interval of about ten minutes, a remarkable trans formation (X-curred. The long. dark flocculus, which had been gradually changing in form and position, was suddenly drawn into the spot. As Fig. 2, Plale \'ir. illustrates, the whirls were very conspicuous on the preceding day. A series of photographs, nine of which were made on negative No. 4201, 1>etwcen 4" 48" 09" p.m. and 5" 13" 54' P.M.. and one, showing the entire disk, on negative No. 4202. at 5" 22" P.M., records the changes which took place (luring this time, These photographs were taken by Dr. C. E, St. Joiix, who joined the observatory staff in May, and is sharing witli me the observational work with the five-foot spectroheliograph during Mr. Ellkrman's absence on vaca- tion. Three of these have been selected for reproduction. Fig. I, Plate \'III, is enlarged from a photograph made Jit Publications of the 4'' 58"" 16* r.M. (time of transit of spot across collimator slit of spcctroheliograpli). At $^ oi"" 2i' the large, dark tlocculus is apparently unchanged in form. At s"* 04° 21' a photograph, which is not quite so well defined, gives no certain evidence of change. The next photograph, made at ^ 07" 06". clearly shows the development of a fork at the eastern end of the flocculus, with traces of a very faint curved extension toward the larger spot. The position of the end of the fork (C), as measured on this photograph, is given below, but the extension is too faint to be measured with certainty. The next photograph, made at 5" lo* 52'. shows the fork and part of the extension, but the definition is poor and the position of the end of the extension uncertain. The last photograph on this plate, made 3( ^h j^id -_j»_ J5 reproduced in Fig. 2. Plate VIII. This admits of fairly satisfactory measurement, the results of which are given below. The spot region on negative No. 4202. made at 5" 22" P..M. (time of transit of spot), is reproduced in Fig. I, Plate IX. Here the definition and contrast are also poor, but the extension, reaching nearly to the spots, is sufficiently well shown, as well as a dark flocculus which developed southeast of the smaller spot. With the aid of the monocular attachment of the stereo- comparator. I have made a careful examination of all the photographs, and Miss W.\re has measured the positions of the long, dark flocculus with the heliomicrometer. If we call A the western extremity of this flocculus, S its eastern ex- tremity, and C its point of nearest approach to the spot, we have the following resuhs of the measurements, which also include the positions of the two spots: — ^^H TABLE I. eiMive No. Uale. Poinl. Uliludc. 4176 May 29, 1908 4i> 26" P.M. A B B' Spot Spot 46 .7 45-8 44 .4 5'.8S 13 .6 12 .8 4189 J,me T. 1908 (1* JO" AM. A B Spot Spot .1 .gw ■ 3-oE 8 >) 5 .5S 1-i 1 PLATE IX i Fifl. I.— Sitn-Spot and Hydrogen (Ha) Floccuu 1908. June 3. ^hijoi p. u. Scale: Sun's D[ameter = o.j Mclcr Fm. J.— Scn-Spot jvkd Hydhoorn IHoT) Tw>C'TO\.v rpoS, Junej.ai'ij'" A. M. Sca\f. Sun's Ow-meVw =Q s'iA.c' Astronomical Society of the Pacific. 213 Table I-^-Continued. Negative No. Date. Point. Longitude. Latitude. Remarks. 4193 June 1, 1908 A 9^7W 4°.0S 5ho8n»p.M. B 6 .4E 12 .9 Spot 3 .5 3 .0 Spot not measurable. 4196 June 2, 1908. A 16 .9W 5 .5S A and A' are the 6*» 10™ A.M. A' 16 .2 4 .5 two extremities of B 2 .9 12 4 western end of floc- Spot 2 .8 2 .8 culus. Spot 4 I 3 I 4201, June 3, 1908 A 38 .3 w 5 .8S Exp. 5. 5hOin»2I*P.M. B 23 .9 II .1 Spot 22 .5 2 .6 Spot 24 .2 2 .7 4201, June 3. 1908 A 35 .8W 8 .2S Exp. 6. 5h04n»2I«P.M. B 23 .6 II .2 C 25 .5 II .1 Spot 22 .5 2 .6 Spot 24 .4 2 .8 4201, June 3, 1908 A 35 .9 W 8 .iS Exp. 7. 5»»07"o6»p.M. B 23 .5 II .0 C 24 .0 9 .2 Spot 22 .5 2 .5 Spot 24 .4 2 .7 4201. June 3. 1908 A 35 .5 W 8 .oS Exp. 9. 5**i3°54"PM. B 23 .6 II .0 C 23 .6 6 .2 Spot 22 .6 2 .6 Spot 24 .4 2 .7 4202 June 3, 1908 C 2$ .oW 3 .5S C approaches east- ern spot. gh 22™ P.M. C 23 .8 3 .4 C approaches west- em spot. Spot 24 .5 2 .6 Spot 22 .7 2 .5 If we now take the measured differences in longitude and latitude of the large spot and the points A, B, and C respect- ively, and compute the corresponding distances, we have the results g^ven in Table II: — 214 Publications of the •/. c 9 '*? t *? 1" ^7 - - o ov *" I k^ ^iM ^^ • »• I ^^ ^ ^* c ^ I I' I II u b o rr tT f*; fO • • • • OC 00 X OC tf tx « i «n • • • ■ -T CJ *>! N •/, • *: ir. ir, 0\ »*: ^Ir ^ • • • • 2 '/: o o cs a 5i + + + + c c f*; ir> ir. C/2 OC 00 o ^ t- o ^ - + 4-+ I II I II u t tt fc **; • ■ • • OC « OC X 4- + -f- + U 29 r^, lO «0 ir. s. o y. (N| r>| „ .^j „ l-f-r + -f-f- -|-+-h + I — c c — c -^ c -1 I I I II ; li - ' o ^^t-r-^i- ccco .r o ■ ■ " ■ /. ^, «, r^ ,s, ,v^ -f — _ _ < -f- f- -h -[- + +4-4-4- ?• ^ ^ ?• ^ p: s r^ ^ — < - < 1^1 -^1 0 ^'■. ^ r. 9- ^ - - -t i>^ <-^, 'N n I "^ - - C C C - "» T O ""• C I \r. \r. \r. \r. \r. w - - ^\ ^ ,r', -' i; (5 '«^, .^' :: = z c >< X X X = ^- ^ ^ 3 ^ '•' '•' '•' fiJ s <^« »^ »-^ — » ^ ""■ "^ -• C C- '^, C - 'off° \. u. Scale: Sun's Diameter- □ ,j MeliT Fig. I,— Sun-Spot anb H\ii»ooMt VHii.> 5uict\;v\ yoS, June 5. jh ig^" p. u, Sca.\e; Sw' s OvMncVti - Q ■ i "^"^^ 1 J ^^^^a J THE Nb:W VUHK ^^H PUBLIC LIBRARY ^H riLDEN FOUNOkTIONI ^^^^ m J Astronomical Society of the Pacific, on June ist to approach the spot, and continued to do so the sudden change occurred on June 3d. Up to this time velocity, instead of showing signs of acceleration, was parently retarded, but the changing form of the flocculus leaves this point uncertain. On the photograph of May 29th (No. 4176) the whirl is most conspicuous north of the spot, where its extreme distance is about equal to that of the west- ern end of the large flocculus. Apparently, however, the flocculus did not fall completely under the influence of the vortex until June ist, when its eastern extremity was 11°. 4^ 140,000"" from the spot. The fact that the minimum distance of the western end always exceeded this quantity may account for its escape. In view of the nature of the phenomena described in this paper, and the fact that evidences of whirls or radial structure have been shown, in connection with several different spots, on a large number of Ha photographs, one is greatly templed to enter at once into a discussion of the sun-spot theories of Faye, Reye, Emden, Halm, Eckholm, Bigelow, etc., all of which assume the existence of cyclones or vortices within the photosphere or the solar atmosphere. It is the part of pru- dence, however, to defer such discussion until our daily in- creasing supply of photographs is considerably enlarged. Moreover, I have devised improved methods for comparing photographs, which should facilitate the identification of ob- jects for measurement, and experiments are also in progress with the purpose of bringing more clearly before the eye the nature of the changes which take place within the vortices. A simple kinetoscope has been advantageously used to observe the rapidly changing phenomena of June 3d, and more elaborate apparatus of tiiis kind will soon be available. It may be well to direct attention, however, to certain points which have been noted : — (t) In the series of photographs (on negatives Nos. 4201 and 4202), which shows the large flocculus in the act of being drawn into the spots, the small flocculi near the spots remain almost unchanged in position, perhaps because of diiTerence of level. (2) Except in the case of the large flocculus, attempts to detect evidences of motion toward the spots have not yet proved successful, even along apparent lines of flow. 1 ) until ^^1 ne the ^H IS ^H cculus ^^1 { 2qth ^^B 21 8 Publications of the ^3) Negative No. 4i' reproduction, though the bright flocculi should be somewhat stronger. Plate X, Fig. i. Except for a defect in the photograph, the bright flocculi surrounding the spot are fairly well shown. In other parts of the figure, however, the background comes out too bright. Plate X. Fig. 2. This is a fairly satisfactory reproduction, though the background is too bright in various places. SOLAR X'ORTK'R.S AND THK ZEEMAX EFFECT. Bv Gk(»rc.k v.. Hale. In a ])revions paper I have described and illustrated the vortices surroundinj^^ sun-spots recently photographed on Mt. Wilson with the Snow telescope and five-foot spectrohelio- graph.^ While studying the vortices, it occurred to nie that the ra|)id revolution of electrically charged particles in the solar atmos])here should produce a magnetic field within a sun-spot (Rowland effect), if a preponderance of negative or ]K)sitive ions be assumed. Such a condition might result from the emission of corpuscles by the photosphere,^ or, as rV()fess(^r E. I'^. Nichols has suggested to me, from centrifu- ' "Solar \'ortice«^." Contrihutious from the Mount Wilson Solar Observatory, No. 26, Puhlirations A. S. P., No. \2\. 'J. T. Thomson. "Conduction of ?'lcctricity through Gases," p. 164. Aslronomical Society of the Pacific. [gal separation dependent upon differences in inertia between positive and negative ions. Lig^ht received from a spot (vor- tex) at the center of the Sun would then be parallel to the lines of force, and its spectrum should contain Zeeman doublets, having components circularly polarized in opposite directions. Close double lines, many of them previously observed vjsually in spot spectra by Young and Mitchell, had recently been photographed with the 30-foot spectrograph and tower tele- scojw. 1 decided to determine whether such lines show char- acteristic evidences of polarization, and to search for other indications of the Zeeman effect I accordingly commenced work with the tower telescope and 30-foot spectrograph on June 24th. The only grating available for use with this instrument is a 4-inch Rowland, having 14.438 lines jter inch, formerly used in the Kenwood spectroheliograph. Its niled surface utilizes only a fraction of the light from the 6-inch collimator objective, but Seed "Gilt Edge" plates, sensitized by Wallace's process, gave fairly satisfactory spot spectra at A. 6200 (third order) in six minntes. A Fresnel rhomb and Nicol prism were mounted in front of the slit. Beside each spot spectrum the spectrum of the photosphere on either side of the spot, or at the center of the Sun. was photographed for comparison, the path of the light. ^tiirough rhomb and Nicol. being the same for the spot and comparison spectra. On each plate the same region of the (Bpectrum was photographed several times with the Nicol set .at different angles, covering a range of about 90°. The components of the true Zeeman doublet, observed under these conditions along the hues of force of a magnetic field, should change in relative intensity as the Nicol is rotated. When the spot was near the limb the results were uncertain, biit when it reached a point about 45° from the center of the Sun the appearance of the doublets seemed clearly character- istic of the Zeeman effect, the relative intensities of the two components being reversed by rotating the Nicol. More than thirty lines showed such an effect in the region X6230-A5241, In many cases these are not doublets, but there was a slight shift of the lines to the red and violet .respectively, when the Nicol occupied two positions from 45° r|o 90^ apart. This would appear to indicate that light from 222 Publications of the the edges of these spot lines is circularly polarized in opposite directions. If so, the displacements are similar in character to those detected bv Zeeman in his first observations of radiation in a magnetic field. In order to determine whether the observed phenomena are to l)e regarded as true Zeeman eflfects, I have made a large number of photographs with the above-described apparatus, showing various regions of the spot spectrum from red to ultra-violet. These prove conclusively that the changes in relative intensity and position of the lines are due to the rotation of the Nicol. The results are consistent among themselves, — the Nicol in one position reducing the intensity of all the red components of doublets, while in the other position it reduces all the violet components.* Moreover, if the stronger component of a doublet appears, for example, on the red side, the single lines in the same spot spectrum are displaced toward the red, and vice versa. As a great number of spot lines show these displacements, it is necessary to inquire whether they may result from un- symmetrical illumination of the grating, caused by rotation of the Nicol. This appeared improbable from the first, since the displacements were determined with respect to comparison sjH'ctra formed by solar light which passed through the rhomb and Xicol under precisely the same conditions as obtained in the case of the spot. An excellent test is afforded by many telluric lines in the red, which are not shifted by rotating the Xicol. The lines of the cyanogen fluting at A 3883, photo- Li rai)hcd in the fourth order, also show no displacement.- It is well known that the lines of flutings are not affected in a magnetic field. So far as I am aware, the only means of trans forminir a single line into a doublet, having com]>onents circularly polar- ized in op]K)sito directions, is a strong magnetic field. It thus ai)pcars probable that a sun-spot contains such a field, which gives rise to doublets and to widened lines in the spot spectrum. ' rii( re ir.ay l)C n few ('\c«ptioii«% \o \\\\<, rule, such as laboratory ex|K'rieucr '.V'.uild lead us to expect. -Three liiic^ in tlii^ t^uiiiK'. which I have measured on negative T \^2. sljmv a in«;in rel.itixe (li^Illal etinMit of o. 14 Atijestroins, corresponding to a rotation of the Xicol through O" . This i'" much Ic^s than the displacement of the spot litir*.. atid withiti the error of measurement. Astronomical Society of the Pacific, 223 It should be mentioned that few doublets appear on the plate in the blue and violet, while many conspicuous ones are found in the red. Preston and Runge have shown that for lines of a given spectral series the ratio - ., is a constant, but A- it is also true that wide doublets have been observed in the more refrangible region of metallic spectra. Why these do not appear in sjx)ts, if a magnetic field sufficiently powerful to produce red doublets is present, cannot now be answered. The separation of the components of many doublets, as measured on the photographs, ranges from 0.018 to 0.216 Angstroms. All of these lines, and many of those which are merely shifted by rotation of the Nicol, will be studied in our laboratory with the aid of a large Du Bois magnet, which is fortunately available. In this work the Zeeman effect will be observed parallel and normal to the lines of force, and at certain intermediate angles, corresponding to various positions of spots on the Sun. It is interesting to note in this connection that lines which appear to be double in some of our spot photo- graphs are triple in others. Mitchell illustrates an excellent case of this sort (observed visually) in the Astrophysical Journal, Vol. XXIV, p. 79,^ where a line which is double across the umbra and one side of the penumbra of a spot is triple across the opposite side of the penumbra. This may perhaps be due to the fact that the line of sight passed through an inclined vortex, parallel to the lines of force in one case and normal to them in the other. These results suggest many possible subjects of investiga- tion, some of which I am preparing to attack, in conjunction with our daily photographic observations of the solar vortices. The direction of the whirls, whether right-handed or left- handed, is a matter of prime interest now under examination. The question naturally arises whether terrestrial magnetic storms, which are known to be closely related to sun-spots, can be caused, directly or indirectly, by solar magnetic fields. If the work now in progress should establish the existence of such fields, it would become necessary to make systematic rec- ords of their areas, intensities, and polarities, in all parts of the ' This paper contains many visual observations of the double lines in spot spectra. 224 Publications of the Sun, for comparison with simultaneous records of terrestrial magnetism, before definite conclusions could be drawn. If spots like those on the Sun are most numerous in the later stages of a star's development, it is conceivable that they may cover a large part of the disk of certain red stars. With sufficient dispersion it might therefore become possible to detect Zeeman doublets in the spectra of these objects. As a fixed spectrograph of great power is being provided for use with our (yo-'inch reflector, now nearing completion, I ho|)e to make the necessary tests this autumn. A more complete account of the sun-spot work, giving meas- ures of the doublets and various other data, will soon be pub- lished in the . I stro physical Jounial. Mt. Wilson Solar Odservatory, July 3, 1908. PLANETARY PHKNOMKXA FOR SEPTEMBER AXD OCTOBER, 1908. 15v Malcolm McNeill. I'HA^FS OF THK MOON, PACIFIC TIME. ViT>{ Q-.iartcr. . Sci)t. .^, ij'' 51"' 1' M. l''irst Quarter. .Oct. 2, I0'M4'" p.m. J'lill Moon " 10. 4 23 A.M. Inill Moon ** 9. 1 3 p.m. Last (Jnarlcr.. . " 17, J 33 a.m. ' Last Quarter. . . '* lO. 7 35 p m. Xew .Mi)on. . . . " 2^, ^> 59 a.m. .VewMoon '* 24.10 47 p.m. 'I'he aiitiininal e(|iiitiox, the time when the Sun cros-^es the e(iiiat()r from north to south, and autumn begins, comes on September 23(1, at 3'' .\.M., I^iciiic time. Mercury will not be in i^ood position for observation durini^ September and October. It passed superior conjunction on Auj^aist 2()th and became an evening star, but as its distance from the Sun increases its motion also carries it far u^ the south of the Sun, even more than is normal for eastern elon- gations in the autinnn. it reaches greatest east elongation on ( )ctober 4th. This distance, 25" 34', is considerably greater than the average greatest elongation, but the planet is at this time more than i 1 S(mth of the Sun. So the planet does not remain above the horizon as much as an hour after sunset. Astronomical Society of the Pacific. 225 and there is little chance for naked-eye visibility. Within a week after the time of greatest east elongation Mercury, as seen from the Sun, reaches its most southern point, and this fact, as stated before, has a considerable effect in shortening the interval between the setting of the Sun and of the planet. At the time of greatest elongation the interval is alrhost always more than an hour, but at this time it is only about fifty minutes. After the time of greatest elongation the planet moves toward inferior conjunction, reaching it and becoming a morning star on October 28th. Venus is a morning star, reaching greatest west elongation on September 14th. On September ist it rises a little more than three and a half hours before sunrise, or a little before 2^ A.M. This interval increases about a quarter of an hour by the time of greatest elongation, and after that time it diminishes slowly, but up to October 31st is not less than three hours and one half. When Venus and Mercury reach their greatest west elongations in the autumn they are in favorable position for observation as morning stars, since they are then far to the north of the Sun and the interval between the rising of the Sun and of the planet is large. In like manner east elongations of these planets in the spring months give a good chance for observation as evening stars. Venus and Jupiter are in rather close conjunction on October 13th. The least distance between them is 36', and Venus is south of Jupiter. Both planets are below our horizon at the time of closest approach, but the distance will not be greatly in- creased by the time they come into view on the morning of October 14th. Mars passed conjunction with the Sun on August 21st and became a morning star, but does not move far enough away from the Sun to become visible in the morning twilight until October. At the end of October it rises about two hours before sunrise, and it may be seen without much difficulty in the morning twilight. As it is now only about as bright as the pole star, it can not be seen as near the Sun as Mercury can. Mars reaches its aphelion on September 3d, a few days after the time of greatest distance from the earth, but the distance from us docs not vary much until after October ist. Until then it remains about 248,000,000 miles. During October it 226 Publications of the Astronomical Society, &c. lessens by about 6,000,000 miles, — not enough to cause much increase in the brightness. Mars excites general attention only when near opposition. These oppositions occur about once in a little more than two years. But during all times, except for a month or so near the time of conjunction, the planet is in plain view and can be easily seen by any one who looks for it in the right place. Jupiter passed conjunction with the Sun on August 17th and became a morning star. By September ist it rises about half an hour before sunrise, — too short an interval for easy visibility, even though it is one of the brightest planets. It soon, however, draws away from the Sun far enough to be readily seen, and by October ist it rises about 3^ a.m., and shortly after i** 30™ on October 31st. During the early days in September it is very close to the first-magnitude star Re^i!;ti!us, the brightest star in the constellation Leo. It is mov- ing eastward and southward, covering about 12° during the two months' period. Saturn comes to opposition with the Sun on September 29th, and is therefore above the horizon nearly the entire night throughout September and October, passing the meridian at about 2^ A.M. on September 1st, at about midnight on October 1st, and before lo*" p.m. on October 31st. It is moving west- ward in the constellation Pisces, about 4°, up to the end of October. The apj^arent breadth of the rings diminishes per- ceptibly the ratio of minor to major axis, changing from one cij^luh at the heixinninjj;' of September to about one eleventh at the end of Octol)er. This diminution will soon cease, and the rini^s will broaden (nit again before the end of the year. Urajius is in fair position for observation, passing the merid- ian at 8^ iq"" P.M. on September ist, and at about 4^ 15"' p.m. on October ^ist. It is nearly stationary in the constellation SaL^ittarius. a few degrees north of the easternmost star of the '* milk-clipper" grou]). The nearest moderately bright star is TT SiJi^ittarii (a small fourth-magnitude), and the planet is about i^ west and 2'^ south of this star, in the direction of the howl of the clip])er. Xcptujic rises shortly after 1*' a.m. on September 1st, and at about 0'^ 15'" i' ^i- on October 31st. It is in the constellation (Jriniiu. N'OTES l"ROM PACIFIC COAST ODSERVATORIES. The Radial Velocitv of a Oriokis. In view of tlie dose connection between variations in llie luminosity and in the radial velocities of stars, the disputed question of the variability of a Orioms suggested that it would be of interest to examine the radial velocities which have been found for this star. Five plates taken with the Mills spectro- graph in its earlier form had given velocities in 1896-98 between + '7-7 and + 19.4"". Before the autumn of 1907 three more plates had been obtained with the same instrument in its new form, and these had been only roughly measured. The result of more careful measurement and reduction was to make it practically certain that the velocity in 1906 January was 4 or s"" in excess of the values previously found. When this was known Dr. Cami'Iikli. very kindly allowed sjjectro- grams to be obtained on a large ntynber of nights, and an even longer series of plates would have been secured had the weather not interfered. The plates from 5035F on have been only provisionally measured, but care has been taken not to introduce any systematic difference as compared with the earlier reductions, and the accuracy of the measures is suf- ficient for its purpose. Two spectrograms of a Orionis had been obtained in 1903 by Professor W. H. Wmr.nT while in charge of the Southern Mills Expedition. These plates he was good enough to meas- ure for me, taking special care to make the reductions uniform with the system adopted by Dr. Campbell for his earlier plates. Dr. Kl'5tnf.r's recent paper (Astrophysical Journal, 27, 301 ) contains four results for a Orionis obtained in 1905-06. These may have a small systematic difference from the Mom.'M. 228 * Publications of the Hamilton results, and it seems likely from a superficial exam- ination of the velocities of the few stars of this type contained in Dr. Kistner's list that in fact the Bonn measures are about 2*"" in excess of those secured on Mount Hamilton. All the available results are collected in the table, an inspec- tion of which can leave little doubt but that the radial velocity of a Or ion is is variable. Generally speaking, the velocity seems to have tended towards a minimum about the year 1898 and to have reached a maximum about 1905 or 1906. In spite of the uncertainty as to any systematic correction which the Bonn results may require to make them comparable, they at least confimi the larger velocity derived from the only Mills plate obtained in 1906. I^Vom that date the velocity seems to have slowly decreased, without, however, falling to the level of the values which prevailed in 1896-98. If the fact of the variable velocity be admitted, it is difficult to draw from the present data any certain conclusion as to the period and nature of the motion. The general variation indicated is one of long period, certainly of many years. But there are indications of irregularities of shorter period about which it is hard to decide whether they are real or s])urious. The results ()l)taiiK'(l in the last two months of i<)07 sug^rest a fairly continuous decrease of the velocity of about J**"'. ( )n the other hand, tlic fourteen plates obtained between i()o8 January 5 and April i<) all fall within a range of \.2^''\ which, in view of the exi)e(litious nietlu)(l of reduction adopted, must he Considered a very satisfactory representation of uniform motion. ( )n the whole, the star seems to deserve contiiuied and careful attention. I'nder the circumstances, aOrio)iis is not a suitable star for use in a deterniination of the Solar Parallax. It is included in the workini;- list of tlie Ca])e Observatory ( .Istrof^hysica! Jininiiil. 27, i^)^ ). tt /- t-» H. C . Phl'MMI-.R. n^oS July. I'l.-itr. l);.to. \il. Kc.l. l.y Si>ectn>v;r.i|-li. 17^. n lSc;f. Oot. .^ - i iS -T- 17^ 1 '. t K V S • • ()io A iS<>'^ Jan. 25 -^ 1.^.4 ( WlIH! I 1. •• ^44 A I-VI). 14 - 177 * 4 • Astronomical Society of the Pacific, 229 Plate. Date Vel. Red. by Spectrograph. 3063 D 1903 Dec. I + 19.36 H. C. P. Second Mills 3078 F 7 + iS.i\?. • « t* 4160 B 1906 Jan. 26 + 23.97 i« •• 5018 D 1907 Nov. I + 22.56 • « 4 ft 5019 E • I + 22.74 • 1 • • 5029 D 7 + 23.45 • « ftft 5035 F 10 + 21.9 «» • ft 5046 D 15 4-22.0 41 • ft 5047 A 21 + 21.4 • • «• 5051 B 2^ 4- 21.2 ft« ftft 5052 D ;23 4-20.4 t« • ft 5057 H 24 4-21.7 »« • ft 5065 H 26 4-22.8 *• • ft 5071 D 29 4- 20.1 • m • ■ 5073 A 30 4-20.3 • • ftft 5078 B Dec. 17 4- 19.1 «• • ft 5084 C 22^ 4-20.9 »« ftft 5089 C 1908 Jan. 2 4-19.2 «• • « 5096 D 5 4- 21. 1 «• • ft 5097 H 4-20.7 • • • ft 5111C 9 4-21.9 • • ft • 5118 A 28 4-20.7 «• ft ft 5»38B F'cb. 17 4-21.4 • ft ftft 5205 A Apr. I 4-20.7 * • • 4 5207 A 2 4-20.9 *• • t 5218 H 6 4-20.9 ft* ftft 5219 A 8 4-21.2 ft* ft« 5224 B 9 -h21.6 ft* «• 5227 E 12 4- 21.0 • • ftft 5228 A 16 4- 21.0 • ft ftft 5234 A 17 4-21.9 ft« • ft S2z(y A 19 4-20.8 • < • • (4III) 1903 Sept. 15 4-20.72 Wright Sotithcrn Mills (42111) Nov. 11 • 4- 20.32 •• •• (356) 1905 Feb. 9 4-27.89 ZrRIIELLEN llonn (367) Mar. I 4- 25.30 • ft • ft (533) Dec. 30 4-26.46 *« • • (591) 1906 Mar. 4 4- 26.64 • ft • ft 230 Publications of the A DiSTURBKI) RE(noN IN THE CoRONA OF JANUARY 3. I908. In his study of the solar corona of April, 1893, as photo- graphed by the Phoebe A. Hearst Expedition from the Lick Observatory to Chile, Professor Schaeberle was led to the conclusion that the inner ends of the coronal streamers coincide in position with disturbed areas in the photosphere of the Sun. Tracing the streamers inward to the Sun*s surface he located six chief centers of origin. On comparing these results, obtained from the coronal image alone, with the photographic record of the uneclipsed Sun made by Professor Hale in Chicago on the day of the eclipse, Professor Schaeberle noted an agreement between the points determined by him and the disturbed areas shown on the photograph of the uneclipsed Sun. From a study of his and previous coronal photographs he concluded that the origins of the coronal streamers are, in the main, confined to the spot-zone regions. [See Contributions from the Lick Obsen'otory, No. 4, pp. 108- II3-1 In Lick Obscn'atory Bulletin, Nos. 9 and 18, Dr. Perrine, in charge of the Crocker Eclipse Expedition to Sumatra in i(;oi, described an area [in space a volume] of unusual dis- turbance recorded on his photographs of the corona. A num- ber of streamers appeared to radiate from a common point, situated Ix'hind the Moon, as if thrown out by an explosion at the pcMHt, though it was not contended or suggested that an ex])losi()n had actually occurred. On comparing the esti- mated position of the invisible vertex with photographs of the uneclipsed Sun obtained at Dehra Dun, India, on the day of the eclipse and on several days preceding and following the eclipse, it was found that the apex of the disturbance was apparently coincident with the large and only sun-spot shown on the entire series of Sun photographs. It was impossible to doubt that the coronal disturbance was intimately connected with the sun-spot. The large-scale ])hotogra])hs of the corona of August 30, i^K)5, secured by the Crocker Expeditions to Spain and Egypt likewise showed an extensive region in the southeast quadrant C(^niposed of ]>roniinent streamers which appear to radiate from a common point. The apex of the cone of disturbance Astronomical Society of the Pacific, 231 projected upon the photographic plate is some distance within the Sun's Hmb. The apex was, no doubt, near the photosphere. The estimated position of the vertex on this occasion fell fairly near, but not in coincidence with, a prominent sun-spot shown on photographs taken at Mt. Hamilton on the day of the eclipse. Tracing the position of the spot back through one revolution of the Sun, it was found that the sun-spot was on August 3d in the estimated position of the vertex. Just what weight should be given to this observation, as related to the question of a close connection between coronal structure and sun-spots, is uncertain. The detailed measurements are published in Lick Observatory Bulletin, No. 115. Lick Obsen'otory Bulletin, No. 131, which was sent to the printer several months ago and is now ready for mailing, describes brieflv a similar con« of disturbance in the corona observed by us on the P'lint Island photographs of January 3, 1908. Recent careful measures of the position of the vertex place it at Position angle, 75°o E- of N. Distance from Sun's center, I3'.7 It should be said that the disturbance, while on a very large scale, does not fix the position of the vertex so definitely as in the case of the 1901 disturbance, as the streamers seem to radiate from a small area or perhaps from several points near each other. The photoheliograph camera of the Lick Observatory was dismounted in the fall of 1907 to make way for the new fire- proof building, and photographs of the Sun at and near the time of the eclipse could not be secured here. At our request, Director Hale of the Mt. Wilson Solar Observatory most kindly supplied the deficiency by loaning photographs of the uneclipsed Sun taken on January 3, 4, and 5, i()o8. There was a region of great apparent disturbance near the east limb, in north latitude io°d:, shown especially well on a spectroheliograph IJ^ negative. This region contains five or more sun-spots within a few degrees of each other. P'rom the position of the Sun's equator marked on the back of the photo- graph by Professor Hale, combined with the angle between the equator and the east and west line, we have measured the 232 Publications of the positions of the chief spots of the group for the time of total eclipse, referred to the Sun's center, as follows: — Position Angles. Distance. 7i°.8 E. of N. i3'.4 77 -9 13.2 77 -5 14.8 80 .5 14 .2 82 .0 14.8 The estimated position of the vertex falls within the spot group ; and it is scarcely possible to doubt that the disturbance in or near the photosphere is intimately related to the disturbed conical volume of the corona. Whether the coronal and photo- spheric disturbances are related to each other as cause and effect, or, more probably, as foint effects of a more general cause, is not known. The subject takes on renewed interest in view of Professor Hale*s recent discovery of cyclonic motion or vortices in sun- spots and surrounding regions. ^ ^ Campbell, 1908 July 31. S. AlBRECHT. Flint Island Corona. In No. 119 of these Publications appeared half-tone illustra- tions of the solar corona from photographs made by the Crocker Expedition to Flint Island. In No. 120 I called attention to the fact that the prints supplied by an Eastern engraver and printer were inferior to the proof-sheets of the illustrations, and that the printer had made an error in orienting the smaller coronal subject. In view of these facts, acknowledged by the engraver, new ])rints of the two subjects have been supplied by him. They are distributed with the present copy. No. 121. It is advised that members insert them in No. 119 to replace the poorer prints. There is perhaps no astronomical subject more difficult to re])ro(lucc by' mechanical process than the solar corona, and it is necessary to recognize that in the best half-tone repro- ductions the delicate details of structure and the minute dif- ferences of intensitv are almost whollv lost. In view of the Astronomical Society of the Pacific, 233 g^eat injustice done to the merits of the original negatives and the correspondingly erroneous impressions conveyed by the prints on paper, it is a question whether an attempt to publish the coronal photographs by such methods is not a mistake. Every one who proposes to make a careful study of coronal subjects must depend upon the original negatives or copies on elass made from them. ,,, ,,, ^ ^ W. W. Campbell. The Partial Solar Eclipse of June 28, 1908. The beginning and ending of the eclipse were observed with the 36-inch refractor. The object-glass was capped down to eight inches in diameter, and a neutral-tinted glass covered the eye-piece. The times of apparent contact of Sun and Moon were noted, as folIo\Ys: — Beginning. . 6**-20™39P a.m.. Pacific Standard Time. Ending 8 6 13 a.m., It is well known that the estimated time of beginning of eclipse is especially subject to error, for the reason that the observer does not see the Moon's approach, but is suddenly made aware that the Moon has entered upon the Sun's image. Special but unsuccessful efforts were made to see the Moon's limb extending outside of the Sun's image: only that part of the Moon's limb projected on the Sun was visible. Dr. Albrecht also observed the Moon's limb immediately follow- ing the beginning of the eclipse, but could not trace it beyond the Sun's edge. He assisted in all the above observations. The observations were all made through thin clouds. The beginning occurred with the Sun low in the sky and the seeing rated as I on a scale of V (perfect). The end occurred with seeing II. ^^, ^^ Campbell. June 29, 1908. Observations of the Partial Eclipse of the Sun June 28, 1908. The various phases of this eclipse were observed with the object of seeing whether or not the dark body of the Moon could be seen projected against the inner, and very bright, parts of the corona. 234 Publications of the The observations were made with the 12-inch equatorial, stopped down to three inches, using powers of about 125 and 175. A diagonal, plane-glass reflector was used in front of the eye-piece, and as light a shade-glass as possible. Thin clouds covered the sky during the observations, but were not sufficiently dense to interfere with seeing the detail of structure in spots. No evidences, whatever, of the corona were seen. The contacts were observed as follows: — First Contact, 1908, June 28. . 2^ 20"^ 3c/ G. M. T. Last contact, 1908, ^June 28.. 4 6 16 •' It was estimated that geometrical first contact occurred two seconds earlier than the above time, which is the time when the contact was certain. The time of the last contact observation is that of the disappearance of the lunar limb, which is practically that of geometrical contact. A high, gusty wind blew from the north during the observa- tions, weakening somewhat toward the end. The seeing was extremely bad during the early part of the observations, but improved very much before last contact. q p Perrine Mt. Hamilton, Lal.. June 29, 1908. TiiK Okiuts ok riiL-: SiMccTRoscorrc Binaries p Hercvlis AND o Leonis. P Hcrculis. — This star was found to have a variable radial velocity by Dr. Campiiki.l in 1899. By September, 1902, a >crics of ihirty-lwo spcctroi^ranis had been obtained at Mt. Hamilton, and a determination of thje orbit from this material was undertaken by Dr. II. M. Reksk. Before his investiga- tion was (juite conij)leted, however, he resigned his position in the Lick Observatory, and left in June, h,)03. without preparinjj^ his results for publication. A careful examination of the papers left by Dr. Reese shawed that his work had been carried to an advanced stage, and that little was necessary to put it in a final form and to verify that it rei)resente(l the orbit with satisfactory accuracy at the time when the observations w-cre made. A set of pro- visional elements had been adopted after some trials, and from the e(|uations of conditions based on these elements difFeren- Astronomical Society of the Pacific. 235 tial corrections had been calculated in the usual manner by the method of least-squares. The result of applying these is to give the following final system : — ELEMENTS OF )8//£i?Ct;L75. ' Period, U = 410.575 days ; fi = 2^17-^ = 0.0153034 T = J. D. 2415500.374 = 1901, April 25, 9^ G.M.T. ^ = 0.5498; <^ = 33° 21' a> = 24° 36^.3 Velocity of system, y = — 25.52^™ K = 12.782^" ; V = — 19.13 + 12.782 cos u which represent the observations satisfactorily. From them may be deduced a sin i = 60,280,000''° (w + W) sin H =: 0.0519 ( I + ni/m^y where m is the mass of the star whose spectrum has been observed and w' the mass of the other star, the Sun's mass being unity. oLeonis, — ^The variability in the velocity of this star was discovered by Dr. Campbell in 1898. Its spectrum had pre- viously been described as of composite type by Miss Maury. It is interesting to notice that out of a list of eighteen stars so described by her, eight have now been found to possess a variable velocity in the line of sight. Lines of the second spectrum can be recognized and measured separately on the plates except when the radial velocities of the components are in the neighborhood of the velocity of the system. A series of thirty-eight plates had been secured in 1898-1900, and three were taken in the present year with the object of improving the period. The eccentricity of the orbit is certainly very small, and a circular orbit has been adopted. The separa- tion of the two spectra makes it possible to determine the ratio of the masses. The results are as follows : — Period = 14.4980 days Ratio of masses, Wj : Wj := 7 : 6 F, = + 27.07 + 54.05 sm ti{t — T) ^2 = 4- 27.07 — 63.06 sin ;i (^ — T) T = 1899, Jan. 1.477 ; f* = 24^.831 a, sin % ■= 10.775,000^", f«i sin H = 1.302 02 sin 1 =. 12,571,000^™, W2 sin *t = i.i 16 236 Publications of the The comparison of the observations with the results of cal- culation from these figures shows great irregularities in the measures. The measures can be arranged in order of increas- ing inaccuracy thus: (i) the measures of component I when II is separately visible, (2) the corresponding measures of component II, (3) the measures of I when II is not separated. Of ( I ) it may be said that the results are distinctly poor and fall below what is to be expected from a careful measurement of a large number of lines in a single spectrum. The lines of II which can be clearly distinguished on any one plate are few (sometimes no more than two), and comparisons in the second group shows differences which, taken on the whole, must be considered satisfactory under the circumstances. But in the third group the interference between the two superposed spec- tra has disastrous effects on the accuracy. In view of the fact that spectrum II separately is quite inconspicuous in com- parison with I, this is rather surprising, but that the interfer- ence of the spectra is the effective cause is clear because the large displacements are all in the direction of the mean velocity of the system. Thus one plate which shows the largest discrepancy gives a measure -f- 28^", when it should give + 38*^™, for component I. In cases like the one alluded t(^, the superposition of the two spectra does not affect the appear- ance of the lines noticeably, although the inconsistency of the individual lines becomes apparent in the measures. It has not proved possible to isolate lines of the first spectrum which are unaffected by the second. A comparison of the above results has been made with a series of twelve plates obtained in 1905-1906 with the Bonn spectrograph, and discussed by Dr. Zurhellen (Astronom- ische Xachrichtcn, No. 4151). The star is not a suitable one for instituting a comparison, for reasons explained, but there seems to be a satisfactory absence of systematic difference between the Bonn and Mt. Hamilton observations. May, 1908. H. C. Plummer. Astronomical Society of the Pacific. 237 Discovery of Many Small NEBULiE Near Some of the Globular Star Clusters. Heretofore but few nebulae have been known to exist near the globular clusters. It has been pointed out that nearly half of the globular clusters lie in or very near the Milky Way, a region almost devoid of the small, "unresolved" nebulae which have been found so plentifully in non-galactic regions of the sky. Association with Keeler's Crossley photographs led to a suspicion that the regions about these clusters were, on the whole, non-nebulous regions. Just recently, however, quite contrary facts have developed. Upon repeating observations of some of these clusters under the greatly improved conditions now provided by the new mounting for the Crossley mirror, I was struck with the large number of small nebulae on some of the plates. Thus far three of these subjects have been repeated under the improved conditions, viz: — N. G. C. 7078 (Af 15 Pegasi) 16 nebulae recorded. N. G. C. 7089 {M 2 Aquarii) 30 N. G. C. 7099 (M 30 Capricomi).. . 31 The star images on these plates are so sharply defined that it is possible to distinguish the very minute nebulae with ease. On the earlier plates but few of them can be distinguished from the stars, owing to the fuzziness of all of the images. The great majority of these nebulae are little or no larger than an out-of-focus distorted star image. In the course of a study of the globular clusters I have obtained photographs of the majority of these objects within reach of the Crossley reflector. They were obtained with the old mounting and in the experimental stages of the new one. The images are generally poor, but I have examined them for nebulae. On three negatives I have found eight, fifteen, and thirty-two respectively. On several others I have found from one to four. Some nebulae were suspected on nearly all of the remaining negatives, but the images are too poor to decide. They appear to be most numerous about clusters which are farthest from the galaxy. In a few instances, nebulae were found in the edges of the clusters. ti it 238 Publications of the Practically all of the small nebulae found about the globular clusters are elliptical or circular. Those large enough to show structure are spirals. Doubtless the majority of them are ^ , , CD. Pehrine. Mt. Hamjlton, Cal., July 16, 1908. The Difference of Longitude between Lick Observatory AND Mare Island Observatory. At the request of the Bureau of Equipment, Nav>' Depart- ment, Washington, D. C, the Lick Observatory recently determined the difference of longitude between it and the U. S. Observatory at Mare Island. The results have been forwarded to the above Bureau and also published in Lick Obsen^atory Bulletin, No. 130, vol. IV. The observations for clock errors and rates at the two stations were carried out by Professor R. H. Tucker and Mr. R. F. Sanford. Each observed two nights at each station. For time observations the Repsold Meridian Circle of the Lick Observatory was used on Mount Hamilton, while the Stackpole Broken Transit No. 1502 of 2.5 inches aperture was used at Mare Island. The mean of the observed differences of longitude between the two stations when corrected for systematic errors is 2"! 3o^74, with a probable error of zb o^.oi. The value of the longitude of the Meridian Circle of the Lick Observatory adopted is that determined by the U. S. Coast and Geodetic Survey in 1888 and published in the report of 1889 as Appen- dix No. 8. This value is 8^ 6"* 34".8i* west of Greenwich. The resulting longitude of Stackpole Transit No. 1502 at Mare Island is therefore 8^ 9™ 5^55 west of Greenwich. Mt. Hamilton, May 12, 1908. R. F. Sanforix • The Superintendent of the I'. S. Coast and Geodetic Survey, Washington, D. C, has recently called my attention to a later readjustment of longitude within the United States, as a result of which the longitude of the Lick Observatory is assigned the value of 8h 6ni 348.89. The corresponding longitude of the Mare Island Observatory becomes 8h Qm 58.63. W. W. C. Astronomical Society of the Pacific. 2'?9 A New Photographic Plate. Recently a series of tests has been made here to determine the speed of the new "Sigma" plate made by the Lumiere North American Company, Ltd., of Buriington, Vermont. The comparison was made by exposure times between the Lumiere plate and the fastest plates heretofore on the market. A series of exposures on the sky was made with a one-prism spectrograph attached to the 36-inch refractor. The plates were then developed until chemical fog began to appear, with the following developer*: — A B Water, 90o*^c Water, goo^^^ Oxalic acid, i gram Lumiere's formosulphite, 120 grams Pyro, 30 grams Using I part of A, i part of B, 2 parts of water. Designating the Lumiere plates by L and the others by X, we have the following list, arranged in order of density of spectrum, braces connecting those nearly equivalent: — J-V 5' [X2(f \l 2 \l 10 fXio- 1^ 5 /^i5" \l 8 This test appears to confirm the makers' claim that the new plate is twice as fast as any other plates on the market. The grain of the Lumiere plate is somewhat larger than that of other fast plates, but this will be no material disadvantage for purposes where speed is the first consideration. The color curve is about the same as for other fast plates of standard American makes. t^ * t- E. A. Path. Lick Observatory. July 2^, 1908. This developer gives better results than either hydrochinone or dianol. 240 Publications of the Astronomical Society, &c. Personals. The superintendency of the observing station of the Carnegie Institution Expedition to the Argentine Republic having been offered to Astronomer Tucker, the Regents of the University of California were pleased to grant him a three years' leave of absence in order that he might accept the appointment. It is understood that Director Boss of the Dudley Observatory, Albany, who is in charge of the Southern Hemisphere work of the Carnegie Institution, accompanied by Professor Tucker. will sail from New York in August. Mr. William H. Wright, Assistant Astronomer in the Lick Observatory from 1897 to 1903 and from 1906 to 1908, and Acting Astronomer in charge of the D. O. Mills Expedi- tion to Chile from 1903 to 1906, has been promoted to the position of Astronomer in the Lick Observatory. Dr. Sebastian Albrecht, a Fellow in the Lick Observatory during the years 1903-1906, and Carnegie Assistant in the years 1906- 1908, has been promoted to the position of Assistant Astronomer in the Lick Observatory. Mr. R. F. Sanford, for two years past Carnegie Institution assistant in the Lick Observatory, has been appointed by Pro- fessor Boss to act as an assistant to Professor Tucker in the Argentine Republic. Miss A. EsTELLE Clancy, of the Qass 1905, Wellesley College, and for the past two years an assistant in the Students' Observatory at Berkeley, has been appointed Fellow in the Lick Observatory. ^_ ^_ Campbell. GENERAL NOTES. Vacation Pastimes. — Authors do not always realize that a great deal of time might be saved to those who use their books if they would give accurate and exact information con- cerning the works to which they make reference. I have recently had occasion to use Professor Newcomb's work on the Precessional Constant.* In this memoir the author refers a number of times to his own work, "Elements and Constants," but at no place in the memoir, so far as I am able to find, does he give an exact reference which would enable one not familiar with the work to readily obtain it. Now possibly anyone who makes pretense to being an astronomer ought to be ashamed to admit that he is not familiar with this work, but I am obliged to make this ignoble confession. Having learned of its existence, however, I became pos- sessed of a strong desire to see the book. The card index of the University library threw no light upon the subject. As many of Professor Newcomb's most valuable contributions to astronomical science have been published in the Astro- nomical Papers of the American Ephemeris and Nautical Almanac, the next thought was to look through them, but the examination revealed nothing. (Some of the parts of the later volumes are unfortunately missing.) The next thought was to examine Newcomb's "Compendium of Spher- ical Astronomy," recently published by The Macmillan Com- pany. One of the special, and also one of the most valuable, features of this book is the notes and references given at the end of the various chapters. So far as I have examined them these references seem to be correct and exact, except the references to the author's own "Elements and Constants." At no place apparently does he give an exact reference to it. On page 231 of the "Compendium," under the subject of precession and nutation, we find a small table of numerical • Astronomical Papers Prepared for the Use of the American Ephemeris an.i Nautical Almanac, vol. \ ITT, part I. Washington, Bureau of Equipment, Navy Department. 242 Publications of the quantities and a footnote, as follows: "Astronomical Papers of the American Ephemeris, vol. IV ; 'Elements and Constants/ p. 186." Now Astronomical Papers, vol. IV, contains Hill's "Theory of Jupiter and Saturn/' and has nothing whatever to do witl\ precession and nutation. "'Elements and Con- stants/ p. 186/' is very illuminating. On page 249 "Elements and Constants" is again referred to in this abbreviated way in two footnotes, while Oppolzer's classic work is referred to in detail, even to the date of publication. On page 255 we find a reference, " 'The Elements of the Four Inner Planets and the Fundamental Constants of Astronomy,' published by the American Nautical Almanac in 1895," which is presumably the full title of "Elements and Constants," but still gives no information as to whether it was published as one of tiie Astronomical Papers or in the numbers of the Ameriam Ephemeris and Nautical Almanac, or otherwise. Further examination of the series of publications just mentioned re- vealed nothing. Still further search, however, brought a happy result. In Astronomical Papers Prepared for the Use of the American Ephemeris and Nautical Almanac, vol. VI, part II (Tables of Mercury), page i, we find, "The elements of Mercury on which these tables are based are found in the author's work entitled. 'The Elements of the Four Inner Planets, and the Fundamental Constants of Astronomy/ form- ing a supplement to the American Ephemeris and Nautical Almanac for the year 1897, pp. 181-185/' which gives the information which ought to have been given at a number of places where it was not. It is indeed a delightful pastime to spend one's vacation in work of search and research ( ?) of this kind. S. D. T. Notes from **ScienceJ* — Dr. Johann Gottfried Galle, from 185 1 to 1895, professor of astronomy and director of the observatory at Breslau, has celebrated his ninety-sixth birthday. At the University of Indiana W. A. Cogshall has been j)romoted from assistant professor to associate professor of astronomy. Astronomical Society of the Pacific. 243 Professor H. H. Turner, f.r.s., has been elected corre- spondent of the Paris Academy of Sciences in the section of astronomy. At Princeton University Henry Norris Russell and Ray- mond Smith Dugan have been made assistant professors of astronomy. Sir George Darwin, k.c.b., f.r.s., has been elected a foreign member of the Amsterdam Academy of Sciences. The astronomical observatory and library founded in honor of Maria Mitchell, adjacent to her birthplace, on Nantucket, were formally dedicated on July 15th. Professor A. O. Leuschner, Director of the Students' Observatory of the University of California, who has been granted a year's leave of absence, left for the East in June. Most of the year will be spent in Berlin and Paris. During Dr. Leuschner's absence the Students' Observatory will be in charge of Assistant Professor R. T. Crawford as acting director. Comet Encke was rediscovered May 27th, a month after perihelion passage, by Woodgate at the Cape of Good Hope. The cometary objects photographed last December and Jan- uary at Heidelberg, and at first announced as Encke's comet, are now thought to be fragments of it. — Journal B, A, A, A fourth member of the TG or Achilles group of asteroids was recently announced. It is CS, discovered March 25th at Heidelberg, and will probably soon be known by a Homeric name, along with Achilles, Patroclas, and Hector. Special interest attaches to this group because of their approach to the conditions of the equilateral triangle solution in a system of three finite bodies. Each of them moves approximately in a vertex of an equilateral triangle that it forms with Jupiter and the Sun. j. D. M. 244 Publications of the In Astronomische Nachrichfen, No. 4249, Paul Guthnick finds that the variation of brightness of Eros depends on the phase-angle. Eros presents a greater range of phase than the normal asteroid because of the nearer approach of its orbit to the orbit of the Earth. It is also bright enough for meas- urement with ordinarily powerful photometric apparatus. The difficulty of connecting Eros's variation with change of phase augurs little success for similar research with the average asteroid. Taking Svedstrup's mean distance of the "mean asteroid" as 2.65 astronomical units, computation shows its change of magnitude due to phase to be only about 0^.04. Even from Mars the change is only o".io. j. D. M. M. NoRDMANN, of Paris, finds that violet light (wave-length 4300) arrives from Algol sixteen minutes later than red light (6800). In the case of XTauri the delay is three times as great. M. Tikhoff, of Pulkowa, finds that violet light (4300) from WY Persei reaches us four minutes later than vellow IJ&ht (5600) ; and that ultra-violet light (4000?) from W Urscc Majoris follows orange light (6100?) by ten minutes. In 1903, M. Belopolsky found that the orbit of p Aurigar derived spectroscopically from indigo light (4500?) was in advance of the orbit from violet light. In each case, the retardation is greater for shorter waves. Its smallness leads Mr. Gavin J. Burns, writing in Journal B. A. A., 18, 328^ 1908, to attribute it to an extensive atmosphere surrounding the star rather than to a resisting medium filling interstellar space. If due to the latter, we shall probably be able to translate retardation into distance in the case of stars of rapid light change. At present, Algol seems to be the only variable star whose parallax has been determined. Meanwhile, Dr. Sciilesingi:r^ finds that Algol's eclipse is reported about two hours earlier by radial velocity determina- tions in ultra-violet light of wave-length 4200, than by visual observations (of average wave-length 5700 perhaps) : and a similar lag exists in Bklopolsky's- elements of this star. These results evidently demand a different explanation. None has yet been offered. J. D. M. ' Publications of the Allegheny Observatory, 1, 32, 1908. ^ Mitteilungen der I'ulkuiea Stermvartc, 1, 103, 1906. Astronomical Society of the Pacific, 245 The attention of members of the Society is called to the fact that the notice printed on the last page of the Publications has been revised. Royal Observatory, Greem&nch. — The annual visitation of the Royal Observatory took place June 4th, the Board of visitors being constituted as follows: Lord Rayleigh, Mr. H. F. New ALL, Professor W. G. Adams, Professor J. Larmor, Professor Sir J. Norman Lockyer, Lord Rosse, Principal Sir A. W. Rucker, Captain Sir W. de W. Abney, Professor Sir R. S. Ball, Professor R. B. Clifton, Dr. J. W. L. Glaisher, Sir W. Huggins, Mr. E. B. Knobel, Professor H. H. Turner, Professor Sir G. H. Darwin, Rear-Admiral A. MosTYN Field (Hydrographer of the Navy), and Mr. W. D. Barber (secretary). A large number of gentlemen interested in astronomy were present by invitation of the Astronomer Royal, and took part in the inspection of the observatory and instruments. The Astronomer Royal presented his report, which deals with the work of the observatory during the past year. . . . It was discovered last year that the method of illuminating the field of the transit-circle by means of an elliptical annular reflector, lit by an axis lamp, was open to objection, as the tilting of the reflector to different points to produce various degrees of illumination caused a shift in the center of light, and an apparent shift in the wires; it is possible that part of the "magnitude equation*' of faint stars arises from this cause. A uniform central illumination has now been substituted, a small elliptical reflector with a matt white surface being cemented to the center of the object-glass, reflecting the light of a small electric lamp ; change in the degree of light is pro- duced by altering the current through the lamp by a rheostat. This plan has been in use in the Altazimuth for a year with very satisfactory results; arrangements have been made on each instrument to take a few transits by the old method for the purpose of comparison. A new arrangement of wires has also been inserted in the collimators of the transit-circle, thin parallel wires replacing the thick oblique wires in former use. . . . 246 Publications of the The 28-inch refractor has been used for the observation of double stars; 81 were observed with a distance of less than /4", 95 between J/2" and i", loi between i" and 2", 211 over 2". Among these *c Pegasi was observed on fifteen nights, BEquulei on thirteen, and yoOphiuchi on sixteen. Mr. BowYER is taking a special course of observations of this last star, with a view to settling the question of the inequalities in its motion. Observations of the diameters of Jupiter and his satellites have also been made with the 28-inch. With the 26-inch photographic refractor thirty-one photographs of Nep- tune and his satellites have been obtained ; while with the 30-inch reflector Phcche (the ninth satellite of Saturn) has been photographed on sixteen nights, Jupiter VI on thirty nights, Jupiter VII on twenty-one nights, Jupiter VIII on twelve nights, also fifty-four minor planets on 140 nights. Comet rf 1907 (Daniel) on thirteen nights, Comet ^1907 on eight nights. Phoebe is an excessively faint object of the 17th magnitude, discovered by Professor W. H. Pickering in 1898, but it was not till last year that Saturn had come far enough north to pennit the satellite to be photographed at Greenwich. These photographs will be of great use for giving an improved value of the mass of So turn, which is uncertain to a small extent. THE EIGHTH SATELLITE OF JUPITER. The eighth satellite of Jupiter is a new discovery, made at the Royal Observatory by Mr. Melotte. Examining a photo- graph of the sixth and seventh satellites, taken at the end of February, he found an unknown moving body on the plate; looking back, he detected it on eight other plates taken during the preceding month. Since then exposures have been made on every fine night when the Moon was absent, but it has only been possible to photograph the object on four more nights, the last being on April 24th. In addition, it has been observed by Dr. Wolf at Heidelberg, and at the Lick Observa- tory. It appears to be a very distant satellite, at a distance of some sixteen million miles from Jupiter, and with an orbit inclined some 30"" to his. Its period of revolution would thus be two years, its distance from the planet being two and one- half times that of the sixth and seventh satellites and 160 Astronomical Society of the Pacific. 247 times that of the fifth satellite, which is the nearest to Jupiter, so that the range of distances in the Jovian family is much greater than in the Sun*s family of planets. A further point of interest in the new satellite is that it appears to revolve around Jupiter in a retrograde direction, in opposition to all the other members of the family. In this point it resembles Phcebe, the outermost member of Saturn's family; Professor Pickering suggests that the primitive rotation of the planet was retrograde, and that it was subsequently reversed by the action of solar tides; these distant satellites are supposed to have been born before the reversal, so that they are a relic of the primitive order. The new satellite is of the sixteenth mag- nitude, implying a real diameter of about thirty-five miles. Even as seen from the surface of Jupiter it would only be of the eighth magnitude, and so would be utterly invisible to the naked eye. COMETS. Daniel's comet was a very conspicuous object in the morn- ing sky last August, probably brighter than any seen in these latitudes since 1882, and the photographs taken of it show a great amount of interesting detail. The tail wfis fan-shaped, and composed of a number of nearly straight jets diverging from the nucleus. This type has been exhibited by many recent comets. According to Professor Bredichin's theory, the different jets have different specific gravities, and so are expelled from the nucleus with different velocities. Several plates were exposed last winter in the search for Halley's comet, but without success. It is rather unfortunate that the region of search was in the Milky Way, between Gemini and Monoceros, and consequently the background is extremely richly strewn with faint stars, which makes the task of picking up an exceedingly faint object like the comet much more dif- ficult. Next autumn the search will be resumed, with more prospect of success, as the comet will then be only slightly outside the orbit of Jupiter, and many comets have been fol- lowed to a greater distance than that. A large amount of computational work on this comet has been carried out by Messrs. Cowell and Crommelin. It consists of two parts — (i) to ascertain as accurately as possible the circumstances of 248 Publications of the the next return; (2) to carry back the perturbations as £ar as possible in order to test the accuracy of Dr. HindV identifica- tions in a paper he presented to the Royal Astronomical So- ciety some fifty years ago. They find that the probable date of the next return is 1910, April 8, which is six weeks earlier than that given by de Pont^coulant. Unfortunately, the new date means a less fine display in these latitudes, for, though the comet will make a near approadi to the earth on 1910, May 10, it will then be some ao^ south of the Sun, and so will set very soon after him. The conditions in tte Southern Hemisphere will be much more favorable. The other research has been carried back to the year A. D. 760, and on the whole Dr. Hind's results are confirmed, though he is idiown to be ten months too late in 1223, four montfis too early in 912, one and one-half months too late in 837. The most interesting appearance on the list is the famous comet which preceded the Norman conquest in 1066; contemporary accounts and the Bayeux tapestry give a vivid idea of its splendor, and of the lively apprehension it excited in England. Hind was the first to suggest that this was a return of Halley's comet, and his suggestion has now been confirmed beyond doubt. The cor- rections found' for Hind's dates in all cases bring them nearer to the curve published by Dr. Angstrom in 1862, a fact which renders the total failure of this curve for the next return very^ surprising. (The date for the curve is 1913 instead of 1910.) . . . — The London Times. Astronomical Society of the Pacific, 249 Minutes of the Meeting of the Board of Directors Held AT THE Students' Observatory, Berkeley, Cal., on July 10, 1908, at 7:30 p. m. A quorum was present. In the absence of the President, Director AiTKEN was elected temporary chairman. The following were elected to membership: — Mr. James A. Hennesy, 2718 12th St. N. E., Washington, D. C. Professor A. G. McAdie, U. S. Weather Bureau, San Francisco, Cal. The following was elected to institutional membership: — The Daniel Scholl Observatory, Franklin and Marshall College, Lancaster, Pa. The Secretary reported that he had sent the comet medals for the last seven awards and had received the acknowledgments of the receipt of two of them from Messrs. Metcalfe and Daniel. The Library Committee was authorized to purchase one copy of "A Handbook of Learned Societies of North and South America" from the Carnegie Institution of Washington. It was moved, seconded, and carried that the Publication Committee be allowed the sum of $450 for the printing of the remaining numbers of the Publications for the current year. This amount seemed justi- fiable in view of the report from the Treasurer on our finances at the present time. This report, dated July 7th, was received and placed on file. The minutes of the meetings of the Board of Directors of March 28, 1908, held at 5:30 p.m. and at 10:00 p.m., respectively, were ap- proved as printed in Publications, No. 119. Adjourned. Minutes of the Meeting of the Astronomical Society of THE Pacific, Held in Hearst Hall of the Uni- versity OF California, Berkeley, Cal., July 10, 1908, at 8:00 p. m. In the absence of the President, Professor C. H. Rieber, Dean of the Summer Session of the University, called the meeting to order and introduced the speaker of the evening, Dr. R. G. Aitken, of the Lick Observatory, who delivered a very interesting lecture upon the subject, "The Story of a Star." The lecture was illustrated by stere- opticon views. Adjourned. 250 Publications of the Astronomical SoA Mr. CsAU-u BmcKHALTEi , Frtiidm Ur. W. W. CouritLL Firit Vice-PrttiiUM Mr. C. E. RALt Stand Viet-P'ttidtni Uc. F. Moiu Third yict-Ptttiint Mr. R. T. Cmwfou (Studenu- ObMrvaUK^. Berkeley) Stcwtt-j Mr. R. G. AiTKKi. (Mount Hunilton, C»L) Stattmj Mr. J. D. GallcfW.V rrtatanT Board et Dittclon — Anan, Buicebaltei, CAuriEu., Cuwiohd. Cioccti. Ct-SHma, GaUowav. Hale, Moue, Richakmoh, TowMuy. FtNuiiCf Comtnilttt — Mcun. Cuihihg, Ciockes, Aitekh. CemmittH on Pnblkalion — Meuii. Tcwhlxy. Madhill, Uooai. ^^^ Library Commitlci — McHr*. Ckawtoid. Towhlit. Eihauon. ^^H Comtl-Mnlal CemmitUi — Meun. Ci.Hntu. (ei-officio). Pihihe, Towhliv. ^^H due on Che (trBI ttiy of January of eacb year ia elected during Ihe tirx quarter of any yea year; when elielei) during the aeeond uuarMt, aucta duet; wben elected during ihc Uiird c|< of such dues; when elected during ihe last qi: of lueh diiei; provided, however, tbai gne U: provided for shall be collected from any mcc e (hall pay three foonha only of ter. he tball pay one founh unly only of the dnei in this arlKle ually c -oiled a rolled . Any men^Kr desired. 1 by Ihe payment of fiCly dollaiE membera by the vole of the Boara 01 inreciorL . . . s will be Hipplied 10 membcrt. so fac u the slock an ■ payment of two dollari per volume to eilber of Ihe i will be lupplied on the following baiic one dollar lo cenu to dcilera, and fifty cenli lo memben. >nited Slalei may obtain boola from the library of Ihe Secretary at Berkeley tea cents postage for each book apcrs are printed in the PubUcaliiriu ia_ decided dioply should be sent to the chair Stanford University. Califo The Secreury at Beib b of publicatioi I. and for the of tie clmi^ _. c j^y, q( January. March, and Novcmb.., Satgrrtayi of jjioe ind Auguit. Mdnberi who propc t Mount Kan ;kage of envelopes. 1 Ihe Lick Observatory 0 « « \ 1 I ■ i 'J- t '' ' ■ 1 .: " » J 5 e* 1 it ■-.V-A 1^ Vol. XX. San Fkancisco, California, October 10, 1908. No. 122 THE MATURE OF AN ASTRONOMER'S WORK.' Bv \V. W. Campbell, Director of llic Lick Observatory, University of California. For nine years it was my duty and pleasure to show the Saturday- night visitors to the Lick Observatory through the great telescope. Their number varied from none on a few of winter's impossible nights up to a maximum of four hundred and thirty. They came from every civilized country, and all trades and professions were represented. They were mainly of those who go about with eyes and minds open. Views through the telescope, descriptions of the instruments, and explanations of celestial photographs received their eager attention. I was greatly interested in observing human nature under these favorable conditions. My experience with the thirty or forty thousand visitors led me to the conclusions, confinued again and again, first, that, while interest in astronomical sub- jects is latent and could easily be aroused in a large propor- tion of the people, yet the simplest facts of the science, open to frequent observation by everybody, are known to compara- tively few; and, secondly, that the nature of an astronomer's work is seldom understood. At a conservative estimate, the majority of the people are unaware that the stars rise in the east, seem to move across the sky, and set in the west, just as the Sun and Moon do; Ririm. Copyright, igoB, by Tbe Nartl lejur Publications of the liffet^l ur tliai tlic summer and winlcr coiislellalions are differt \'ery few can explain why the form of the Moon changes from crescent to full, and from full back to crescent, or can say wherein the planets differ from the stars. There are regi- ments of joung men, fresh from school and college, who, knowing amperes, ohms, and volts, can tell you all about the lights in your house, but not one word about tlic lights in the sky. The opinion prevails quite generally that an astronomer's duty consists in sitting all night with his eye at the end of iht telescope, "sweeping the heavens." in order to discover new bodies — comets, planets, moons, and new stars: and that this is the end and aim of the science. This view is far from the truth. While we in no way discourage the search for new and unknown objects, and, in fact, hail their discovery with delight, we may say that relatively few professional astron- omers are thus occupied. The great observatories, with their expensive equipments, cannot afford to engage extensively in such uncertain labor. They leave this work to the small observatories and to the private astronomers, or else they make it a very subsidiarj' matter. Thus the Lick Observatory, in discovering twenty-seven comets, has devoted certainly less than the one-hundredth part of its resources to that pursuit. The majority of the unexpected comets are, in fact, found by private astronomers, whose four-inch or five-inch telescopes are abundantly powerful for the purpose. The expected re- turns of periodic comets, on the contrary, are generally detected by professional astronomers. Their mathematical computations tell them when and where to look. New stars (stars which suddenly appear at points in the sky where none were visible before) and variable stars (those whose brightness varies) are, in the majority of cases, dis- covered at Harvard College Observatory, for the most part not by direct search, but as the indirect results, or by-products, of an extensive study of the spectra of the stars for another purpose. A few are detected at private and small observa- tories. Only occasional ones are found at other large ohser*'- atories, and these are usually detected by chance or by ver\' indirect methods. P^ Astronomical Society of the Pacific. 253 It inatiers little if new stars — comets, satellites, nebulae, or variable stars — are simply "discovered." Thai is only the beginning of our interest. There are a hundred million bright stars to be seen in the 36-inch telescope whenever we care to look for them. Of what value is it merely to know that one more star has apjieared? l_'p to the year 1898 some ten thousand nebulas had been discovered at the various observatories, and their positions and descriptions are published in a catalogue of nebulie.' The photographs nf widely distributed regions of the sky, taken in part by the late Director Keeler, with the Crossley reflector of the Lick Observatory, and continued by Professor Pehrivk, indicate that the number not yet discovered, but easily dis- coverable with this instrument, is in excess of four hundred thousand. These can be found whenever we care to under- take the work. The new ones already discovered, by means of plates taken in the past eight years for other purposes, number nearly a thousand. The value of the discovery of such objects is not in the discoveries themselves; it is in the opportunity thereby pre- sented for the thorough study of those objects. If they are simply discovered and not investigated, the science of astron- omy is advanced comparatively little. It is as if Euclid had learned that there is a science of the circle and the sphere, but had nut investigated its laws. It is as if the chemist had discovered that there is an element called oxygen, but had not proceeded to determine its properties: or as if Copernicus had been content, like his neighbors, with noting the existence of the principal heavenly bodies, and had not investigated their motions. There certainly have been no more marked cases of successful comet-seeking than those of Barnard and Perrine during the few years when they gave a small fraction of their time, on Mt. Hamilton, to this pursuit; but the highest astro- nomical prizes of the Paris Academy of Sciences were be- stowed upon them not so much for their discoveries as for the opportunities thereby afforded for the further efficient study of cometary bodies, in which the discoverers themselves played leading parts. ' The nebut* art fnint. cloiidliia fonm. some of which ar» tnasHn of glowing Ik 1 fear that the t'oregoing references to newly discovered bodies have conveyed the impression that our attention is largely devoted to them. This view is erroneous, and 1 hasten to correct it. We do not overloes. but not at all to the unassisted eye. Observations with the Mills spectrograph of the Lick Observatory, the Bruce spectrograph of the Yerkes Observatory, and other similar instruments, have established that at least one star in six is attended hy massive close companions, invisible in the most powerfid telescopes. All these systems, both visible and invisible, call for investigation. There are the variable stars, those thus far discovered num- bering more than two thousand. Why are they brighter at one time than at another? The causes in nineteen cases out of twenty are unknown, and the determination of these causes constitutes a great problem. Half a dozen smalt observatories, extending around the world near the parallel of y)° north latitude, are engaged exclusively in studying the variation of terrestrial latitudes: for it has been shown that the position of the Earth's equator and, therefore, our distance from the equator (our latitude) changes back and forth through a range nf sixty feet. A few large observatories are devoting decades to the accurate measurement of the brightness of the stars. Aslronomical Society of the Pacific. The resources of a dozen observatories are devoted photographic chatting of the heavens, each photograph requir- ing accurate measurement and computation — an enormous piece of work, demanding twenty years or more for its com- pletion. A better realization of the magnitude of the labor involved will be gained, perhaps, by calailating that a dozen observatories for twenty years, oh one problem, is equivalent to one observatory's time and effort for two himdred and forty years. There arc the comets, which excite great public and scientific interest, not only because they arc extremely interesting ob- jects, but because they come close to us. and since they come and go. they must be studied while here. How and where did they originate? What is their composition? What conditions prevail in them? In other words, what \s a comet, and what is its relation to other celestial objects? \nt to illustrate further, it should be said that these lines of work, as well as the far greater number of immentioned ones, all bear upon the solution of the two great problems which at present comjMse the science of astronoiny. These problems, perhaps the most profound in the realm of matter, may be stated thus : — First, a determination of the structure of the sidereal uni- verse: of the form of that portion of limitless space occupied by mir stellar system ; of the general arrangement of the sidereal units in space, and their geometrical relations to one another; and of their motions in accordance with the laws of gravitation ; Second, a determination of what the nebulte. stars, planets. satellites, comets, and other members of the universe really are: what are their chemical constitutions; their physical con- ditions and relations to one another: what has been the history of their development, in accordance with the principles of sidereal evolution; and what has the future in store for them, and for the system as a whole. Obsen-atories supply accurate time signals wherever tele- graph and cable extend. These signals are regidated by observations of stars whose positions have been previously determined by meridian instniments. Many modern boundary to the ^1 liitfs between nations are located by means of observationsT stars whose exact positions in the sky are defined in the star catalogues. The ship's captain ascertains his latitude and lonj^tiide, and llierefore the course of his vessel, by observa- tinns^ of tbc Snn, Moon, and stars, whose positions are pre- pared for him in advance by astronomers, as a result of their extensive observations and extremely laborious calculations. That the main results of the astronomer's work are not so immediately practical does not detract from their value. They are, I venture to think, the more to be prized on that accoimt. Astronomy has profoundly influenced the thought of the race. In fact, it has been the keystone in the arch of the sciences under which we have marched out froni the darkness of the fifteenth and preceding centuries to the comparative light of to-day. Who can estimate the value to civilization of the Copemican system of the Sun and planets? A round Earth, an Earth not the center of the univerise, an Earth obeying law, an Earth developed by processes of evolution covering tens of millions of years, is incomparably grander than the Earth which ante- Copernican imagination pictured. It is of priceless value to the human race to know that the Sun will supply the needs of the Earth, as to light and heat, for millions of years; that the stars are not lanterns hung out at night, but are suns like our own; and that numbers of them probably have planets revolving around them, perhaps in many cases with inhabitants adapted to the conditions exist- ing there. In a sentence, the main purpose of the science is to learn the truth about the stellar universe; to increase human knowledge concerning our surroundings, and to widen the limits of intellectual life. dstronQmtcal Society of the Peteific. PLANETARY PHENOMENA FOR NOVEMBER AND DECEMBER, 1908. PHASES OF THE MOON, PACIFIC TIME. FirsiQiiarter,.Nov. i. G'l&^ii.ti. FullMoon. ...Dec. 7, i"44 FullMoon.... " 7." 58 P.M. Last Quarter.. " 15, i i^ Last Quarter. . " 15, 3 41 p.m. New Moon " aj. 3 50 New Moon.... ■' 2i. 1 53 P.M. First Qvmrter.. " 29. 9 40 First Qiiarier.. " 30, i 44 p.m. There will be a lunar appulse on December 7th. The Moon will just miss passing throngh the Earth's shadow, the nearest approach being 12", at a time when the Moon is rising in the eastern part of the United States. There will be a central eclipse of the Snn on December 23d, but the path of central eclipse lies far to the south, almost in Antarctic regions. The eclipse will scarcely be seen at all north of the equator. It Is noteworthy for the fact that at the beginning and end of central eclipse, which occur at sun- rise anil sunset resi)ectively, the eclipse is annular, and for the regions in the middle of the track, where the eclipse occurs near noon, it is total. This is due to the increase in apparent size of the Moon as it rises higher in the sky, causing a diminu- tion in its actual distance from the place of observation on the surface of the Earth. When the Moon is in the zenith it is nearer tis by abont one sixtieth than it is when on the hori- zon. The maximum duration of totality is only eleven seconds. The Sun reaches the winter solstice and winter begins December 21st, 10" p.m., Pacific lime. Mercury passes inferior conjunction and becomes a morn- ing star on October 28th, and remains a morning star until December 23d, when it passes superior conjunction and . becomes an evening star. It reaches its greatest west elonga- tion, tq" 19', on November 13th,— rather a small greatest elongation, as it occurs only a little more than a week after perihelion passage. It rises rather more than an hour and I one half before sunrise at this lime, and liie interval remri greater than an hour until after Deceniher ist. The planet therefore can be seen in the twilight on clear mornings in the latter half of Novcmlwr. It will l>e too near tlje Sun to be seen in December, except possibly the first few days of the month. Venus rises abont three and one half hours before sunrise on Is'oveniber ist. — that is. at about 3" a.m., — but it passed greatest wed elongatiou about the middle of September, and its distance from the Sun diminishes from 38^ on November 1st to 31° on December 31st. On November ist it was nearly 17° north of the Sun. and on December 31st it is only a little more than 2°. These two causes combined cause a rapid diminution of the time between the rising of the planet and of the Sun, so that at the end of December the interval is only a little more than two hours. It passes perihelion on the morning of November 12th, but this causes very little diminu- tion in the apparent distance from the Sun, for the reason that the orbit of Vants is very nearly circular, and not like the orbits of Mercury and Mars, which are relatively very eccen- tric. Venus and Mars are in rather close conjunction on the afternoon of November 30th, the fomier passing 1° 17' north of the latter. Mars is now a morning star, rising about two hours before sunrise on November 1st, or at about 4*" 30" A.m. On Decem- ber 31st it rises about three and one half hours before the Sun, or a little before 4" a.m. During the two months' period it moves about 38° eastward and 14° southward, through Virgo into Libra, and on November 12th it passes about 3° north of Spica. the brightest star in Virgo. Its actual distance from the Earth has begun to diminish rapidly, thirty-six million miles during the two mouths, and its brightness will in conse- fiuence increase noticeably: but it will not become a conspic- uous object until the late spring of 1909. Jupiter rises at about 1'' 30" a.m. on November ist, and at about 10" P.M. on December 31st. It is in the constellation Leo, and moves about 5° eastward and southward at a grad- ually diminishing rate until December 30th, when it becomes stationary, and then begins to retrograde or move westward. Astronomical Society of the Pacific. 263 Sdlittii is in good position for observation, being above the horizon tinti! 3'' 30" a.m. on November ist, and until nearly- midnight on December 31st, It crosses the meridian at about fji. ^QiB p j,_ Qi^ November ist, and at about 5" 30" p.m. on December 31st. It is in the constellation Pisces, and up to December 7th moves about 1° westward. It then begins its direct motion, and by the end of the month has moved about one half degree eastward. The rings as seen in the telescope appear to diminish in minor axis until December; after that they appear to grow wider, and will broaden out until some lime in the summer of lyog; then for a few months they will appear to narrow again, but the narrowing in 1909 will not be as great as in 1908. There will be, on the whole, a progressive broadening of the rings for seven or eight years. Uranus is in the southwestern sky in the evening. On November ist it does not set until nearly 9" p.m., but by the end of December it has nearly reached conjunction with the Siin and sets only about half an hour after sunset. It remains in the constellation Sagittarius, but moves about 3° eastward away from the "milk-dipper" and ir Sagittarii, which have served to mark it during 190S. Xcpiune rises shortly after 9" p.m. on November ist, and shortly after 5" p.m. on December 3rst, having nearly reached opposition with the Sun. It remains in the constellation NOTES FROM PACIFIC COAST OBSER\'ATORIES. SnME Results ok a Study of the Stkucture of Photo- graphic Films.' It is well known that the discordances found between tlie positions of stars on different photographs, or of dififereiit images on the same photograph, are much greater than the ■errors of measurement alone. Could such discordances be eliminated, the gain in the accuracy of positions derived from photographs would be very great. In my work on the development of methods for deriving stellar parallaxes by photography, this matter of erratic dis- cordances has seemed of first importance, and I have made a study of it. ^H There are several possible sources for these discordances ^H 1. Distortions of the photographic film. ^H 2. Peculiarities of the tele.scope, including its driving mechanism, seeing, etc. 3. The structure of the image formed in the film. The distortions of the film have been investigated by a num- ber of astronomers with the result that such distortions appear to be small and not to account for the large discordances which occur in practice. My own investigations on distortion confirm this opinion, and indicate that they are of the order of magnitude of the uncertainties of measurement. I then adopted a plan which at once eliminated all of the ■conditions of source 2 and threw the responsibility on source 3. It was to copy on the same plate a number of images of t ^ tlications of the Astronomical Society, &c. 265 artificial stars on a pattern plate. The different images were obtained by successive exposures to the pattern plate, shifting the pattern plate a little between exposures. It will be seen that the resulting images should be exactly alike, and that the distances between them should agree exactly, if there is no distortion of the film or no irregularities in form of the images. Measures of distances made on these laboratory plates showed discordances similar in magnitude to those made on actual star-plates. The form and structure of the images on the laboratory plates were next examined under a microscope. It was found that instead of being round and exactly alike, as they should have been, the images were quite irregular in forni, the irregu- larities being great enough to cause such discordances as those observed. These irregularities of form appear to result from vacancies in the gelatine where there are no silver grains. If the ex- posure is sufficiently prolonged, the star-image is opaque in the center, but there is a surrounding penumbra where these vacancies show. It is my belief that these irregidarities of structure are the chief source of the large discordances now found in measures of photographic star-positions. There are also some distortions of the film, but these appear to lie small. At any rate, the structure of the film should be made so uni- form that we can obtain successive images of a pattern star which agree with one another. Then we shall be in a better position to investigate the actual distortions. The illustration herewith is an enlargement to 150 diameters of four images copied by successive contact exposure from a single image on a pattern plate. These four images should all be alike, except for such changes as are introduced by the grain and structure of the film on which the copies are made. It is entirely possible that an increase in the amount of silver in the film will eliminate most of the trouble. A division into finer grains of the silver now present in films should also 1 help materially. I One of our largest dry-plate manufacturers is now experi- 1 menting in the direction of improving the structure of the film, I Publications of the ami it is hopeil that his efforts will be early successful. One of the most encouraging results of these investigations is the apparent freedom of the positions from errors due to the telescope ami seeing, Mt. Hamilton, Cal,, September 26, 1908. C D. PERRItJfti The Orbit uf the Eu;iiTii Satellite of J ui'ithr. ^M From observations extending from January 27th to April 2()th of this year, we have derived a set of osculating; elements of the orbit of Jupite/s eighth satellite, which was discovered last January by Melotte at Greenwich. The results show that the motion is retrograde, the inclination of the orbit plane to the equator being about 146°. The orbit is quite eccentric. 4> being 26°. The sateUite's mean distance from Jupiter is 0.18 (astronomical units). The periodic time about Jupiter is two and a haif years. The oscillating elements were derived by Leuschneh's "Analytical Method of Determining the Orbits of New Satel- lites." which was used here with success in determining the orbit of the seventh satellite. The computation was based upon the supposition that Jupiter is the primary and the Sun is the principal disturbing body. This method then gives the osculating orbit for the middle date used (March 8th), in which the attraction of the Sun as a disturbing body during the period covered by the observations (January a^th-April 29th) is fully taken into account. An ephemeris based ujKin these osculating elements and the perturbations due to the Sun, computed by Encke's method as adapted to this problem by Leuschner, is in preparation. R. T. Crawford, Behkelev .Astronqmic.m. Department. ^- ^- Meyer. Seplcmher 2J, 1908. Note on Comet c 1908. Comet e 1908 was discovered by Professor Morehoui the Yerkes Observatory on September rst. Two orbits of this comet have been computed at the Stu- dents' Obser^'atory. The second set of elements and ephemeris may be found in Lick Observatory Bulletin, No. 139. fER. ^^H Astronomical Society of the Pacific. 267 The comet is moving in a plane inclined 140° to the ecliptic. Its nearest approach to the Sun occurs on December 25th, when it will be eighty million miles from it. At present it is visible in an opera-glass. It is increasing in brilliancy, and will reach a maximum about October 25th. During October its positions among the constellations will be as follows: On the 1st it passes near Beta Cephei; 7th. near Theta Cephei: 13th, near Theta, lotu, and Kappa Cygni; from the 15th to the 31st, through the constellation Lyra, passing about 10° east of l''cga on the 21st. The nearest approach to the Earth, one hundred and twenty million miles, will occur on the isth of October. Stuhla Einahsson, \V. F. Meyer. 1908. \OTE ON THE OrBIT OF jS 6l2. in Lick Observatory Bulletin, No. loi, I pubhshed an inves- tigation of the orbit of this binarj- system which led to a periodic time of 34.4 years. The elements given represented the observed motion to 1906, inclusive, reasonably well, though the run of the residuals gave some evidence of systematic errors, and it was clear that improvetnents could be effected when obser\'ations in the first quadrant became available. The ephemeris for the years following 1906 predicted a steady increase of the apparent distance between the two compo- nents with decreasing angular motion until the companion had reached the position given by Burnham at the time of dis- covery, in 1878. My measures in 1907 and 1908, however, showed little or no increase of distance and very rapid angidar motion, so that the residuals in the two years were, respectively, -!- 22''.3, — o".05, and +50°.! and — o".o8. It was clear that my orbit was unsatisfactory, and this star was therefore used as one of the illustrations in a course on "Double-Star Astronomy," given this year at the summer ses- sion of the University of California. Four graduate students, imder my direction, attempted to improve my published ele- ments, using the data given in Burnham's "General Catalogue of Doublo Stars" and my recent measures. Considerable im- provement ivas effected by reducing Che periodic time lo thirty years, with corresponding changes in the other ele- ments, but llie residuals for the measures of Burn ham and Hall in 1878 were nearly 10^, and for my measures in 1908 over 20". it was also necessary to assume that the earlier observers had greatly over-measured the distance, while I had made as great an error in the opposite direction. We therefore concluded that no satisfactory orbit could be derived from the available data, and Professor LotisE, of Che Potsdam Observa- tory, has recently expressed a similar opinion.' A recent examination of the original measures by Burnuam in 1878 and by Hall in 1878 and 1879 has led me to a new discussion of the orbit, based on the assumption that the com- panion star in those years was not in the first quadrant, as BfRNHAM gives it. but in the third, and that the motion by the year 1891 had amounted to 315°, instead of only 135°, as was then naturally supposed. That this is a valid assumption appears from the fact that Burmiam makes no distinction in magnitude between the two components, while Hall actually gives the third quadrant in his measures in 1879. Otlier observers, too, find little or no difference in the bright- ness of the two stars. This assumption gives an orbit with a periodic lime of only 23.8 years, which represents the observed positions to 1903 .ind those of the last two years within the probable error of measure of so difficult a pair. My observa- tions in 1904. 1905, and 1906 are not quite so well represented, but the star in those years was approaching periastron and the apparent distances were found to be only o".ii, o".io. and "".13, respectively. The angle measures must therefore be regarded as less exact than those in earlier years. It is also true that very slight changes in the elements produce large changes in the residuals in this part of the curve. From these investigations I conclude that the shorter i>eriod, 22.8 years, is approximately correct. The details of the dis- cussion will be published as a Lkk Obsen-alory BuUclm. September. 1508, R. G. ArTKE« iiTothyiikaKsihiin Ohserriiioriumt la Potsdam, At the meeting of the Astronomical and Astrophy.sical So- ciety of America held at Put-in-Day during the latter part of August the following olTicers were elected for the ensuing year : — President — E. C. Pickering. First \'ice -President — G. C. Comstock, Second Vice-President — W. W. Campbell. Secretary — W. J. Hl'ssey. Treastirer — C. L. Docilittle. Councilors — Okmond Stone, W. S, Eichelberger, Frank Schlesinher, W. J. Hump: The I 'arialwn of Latitude. — Provisional results of the Inter- national Latitude Service during 1907. from observations at the north parallel 39° 8', are published by Professor Alhrecht in Astronomischt; Kachrichicn, No. 4253. As in his pro- visional results of previous years. Professor Albrecht has employed the observations, by the six stations, of only those sixty-six pairs v^hich have been observed since the start in 1899. (The other thirty of the ninety-six programme pairs were changed at the beginning of 1906.) The same mean places of the stars have been used a.s in the eariier papers. The deduced path of the pole during the year is traced in the figure here reproduced (from the A'acliriclitcii). which shows the path from 1899.9 'o 1908.0. It appears from the eight years' results that the r-terni, the term that is independent of the longitude, varies in a simple sine-curve of one-year period. The average of the eight annua! .c-curves is almost precisely the sine-curve: 2 = — o".oo2 -|-o".046 sin ((360° -|- iii''.6). in which the time, t, is expressed as a fraction of the year. By this fomnila, j is zero about ten days before the equinoxes, ami reaches its maximum values, — o".048 and -f o".044, about ten days before the summer and winter solstices, re- spectively. The meteorological explanation of the tenii seems plausible, therefore, though it is not at all evident why its zero and maximum values should precede, instead of lagging somewhat behind, the equinoxes and solstices. In a later note in the same number. Professor Albrecht announces the very interesting and important facts, gleaned from the uncom- pleted reduction of data obtained at the two new stations at south latitude 31° 55', that s has the same sign at the south parallel as at the north, and seems to have the same magni- tude. These facts are seen to add weight to the meteorological hypothesis, as we consider the reversal of seasons in the northern and southern liemispheres. Astronomical Society of the Pacific. the Paris Observatory; C L. W. Charlier, director of thi The co-efficients .r and v of the longitude temis were also found to be the same in the southern as in the northern hemi- sphere, so far as could be ascertained at the time of tiie second note. J. D. M. Science for September iSth contains an article entitled, ■"Doctorates Conferred by American Universities." A list of all the doctor's degrees in science conferred in 1908 is given. and, in addition, some statistical studies covering the preced- ing ten years. But one doctorate in astronomy was given in 1908, and that by \'anderbilt University to James Harrison ScARBOKOUGH, whose thcsis was entitled, "The Computation of the Orbit of a Planet." Algol itiriables appear to be composed of bodies of small density. Dr. Ristenpart has deduced (Aslrouomische Xach- richtcu, No. 4250) the densities of ten of them from the ele- ments of their orbits, and finds that they range from one fiftieth to one third that of our Sun, the densest being those of shortest period. — Ohscn'alorw Xolcs from "Science." — Professor Geohiie E. Hale, director of tlie Solar Observatory of the Carnegie Institution, has been elected a foreign correspondent of the Paris Academy of Sciences in the place of the late Asaph Hall. Dr. F. RiSTEfiPAHT, of Berlin, has been appointed director of the Obscr^'atory of Santiago de Chile, as successor to Dr. A. OnBECHT. Sir GEORf;E Howard Darwin, professor of astronomy at Cambridge, has been elected a corresponding member of the Berlin Academy of -Sciences. The Royal Astronomical Society. London, has elected cor- responding members as follows : Dr. E. B. Frost, director of the Yerkes Observatory; J. G. Hagen, S. J., director of the Vatican Observatory; M. Benjamin Baili-aud, director of 272 iltcattons of the Astronomtcal Socteiy, i Observatory at I.iind; ami Johannes Kkanz Habtma the A strophysical Observatory at Potsdam. I'rofessor HL'<.f] von Seeliger, of Munich, has declined a call tu the directorship of the Astrophysical Observatory at Potsdam. j^^| The Earl of Rosse.~The Earl of RossK, a member of the Astronomical Society of the Pacific since i8gi. died 011 the 29th of August last, lie was much interested in scientific work and was a regular attendant at scientific meetings. He was twice elected a vice-president of the Royal Society, of which, as well as of the Royal Astronomical Society, he had been a Fellow since 1867. He was one of the senior mem- bers of the Board of Visitors of the Greenwich Observatory. His latest contribution to astronomy was an attempt to dis- cover whether the rocks composing the surface of the Moon continued to radiate heat after the Sun's light was cut off during a hinar eclipse. The results of this investigation were submitted to the British Association in South Africa, but further experiments are necessary to obtain a definite con- clusion. The father of the late Earl was the distinguished astronomer and sometime president of the Royal Society, who built the great reflecting telescope at Birr. Ireland, by means of which many discoveries of imjjortance were made. NEW PUBLICATIONS. Annak'^ de I'Observatoire Royal de Belgique. Xouvelle Scire, Annales Astronoiniques. Tome X. Observations faitcs au Cercle Meridien de Repsold en 1901, 1902, 1903, 1904. 1905, et IQ06. Bruscelles. 1907. 4tO. vi 4-717- Boards. Annals of the Cape Observatory. Vol. II, Part V, Results of meridian observations of the Sun, Mercury, and Venus. made at the Royal Observatory, Cape of Good Hope, in the years 1884 to 1892. Vol. II, Part VI. Occultations of stars by the Moon, observed at the Royal Observatory. Cape of Good Hope, in the years 1896 to 1906. Edin- burgh. 1907. Folio. Paper. Part V, 109 pp.: price, 3s 6d : Part VI. 60 -|- vi pp. ; price, is 6d. Astrographic catalogue. Greenwich section. Dec. -|- 64° to -1-90°, Vol. II. Measures of rectangular co-ordinates and diameters of star images, Dec. -|- 72° to -|-go°. Edinburgh. 1908. Folio. 996 -i- xlv pp. Cloth. Price, 30s. -Astronomischer Jahresbericht. I.X Band. Die Literatur des Jahres 1907. Berlin. 1908. 8vo, 653 + xxxv pp. Paper. Balcells, P. Mariano. La Observacion Solar. Barcelona. 1908. 4to. 143 pp. Paper. Berliner Astronomisches Jahrbuch fur 1910 mit Angaben fiir die Oppositionen dcr Planeten ( 1 ) — (fioi | fiir K)o8. Beriin. Kp8. 8vo. x + 474 -(-112 + 37 PP- I'aper. BoiiMN, K.ARL. Sur iine equation algebrique remarquable se trouvant en rapport a la mecanique celeste. Astronomiska lakttageiser och undersokningar a Stockholms Observa- torium. Band VIII, Nr. 7. Upsala and Stockholm. 1908. 4to. Ill pp. Paper. Catalogue of 1,680 stars for the equinox 1900.0 from observa- tions made at the Royal Observatory, Cape of Good Kope, during the years 1905-1906. Edinburgh. 1907. Folio. 44 -J- xii pp. Cloth. Price, 3s. Connaissance des temps on des mouvements celeste pour le meridien de Paris, pour I'an igio. Publiee par le Bureau I Jitcanons or ties LoiigitiiiJes. Paris. 1908. 8vo. viii + 810 -}- J pp. Paper. Gray, George J. A bibliography of the works of Sir Isaac Newton, Second edition, revised and enlarged. Cam- bridge. 1907. 8vo. 80 pp. Qoth. HiRAv..\MA, Shin, Effect of color upon the constant of astro- nomical refraction. Tokyo, n. d. ( Reprinted from Tokyo Siigaku-Biiturigakkwai Kizi, 2d Ser., \'ol. I\'. No. 17.) 8vo. 5 pp. Paper. Photohetiographic results, 1874 to 1885. Royal Observatory, Greenwich. Edinburgh. 1907. Folio. 321 -f- xxiii pp. Cloth. Price, 105. Photograph ische Stcmkarten von Johann Palisa und M.vx Wolf, (Atlas of twenty charts reproduced photograph- ically.) Vienna. 1908. 4to. Cloth. Price. 30 ^[arks. Publikationen des As trophy si kalischcn Observatoriunis lu Potsdam. No. 55, Achtzehnten Bandes. dritles Stuck, Untersuchnngeii iiber die Solarkonstanie und die Tem- peratur der Son nen photos phare, von J. Sciieixer. Nr, 58, Zwanzigsten Bandes, erster Stiick, Doppel Sterne von O. LoHSE. Potsdam. 190S. 4to. Paper. Nr. 55.90 pp.: price. 6 Marks. Nr. 58, 168 pp.; price, 11 Marks. UcCETO, Luis. Determinaciones de posicion del cometa Dan- iell en el observatoire Cajigal (Caracas), Caraa 1007. 8vo. 04 pp. Paper. Astronomical Society of the Pacific. OFFICERS OF 1 S SOCISTV. Mr. Ch* Mr. W. W. CaJIpiell First ViciPrtiidtnl Mr. G. E. Hale Stcend VictPrttidiiU Mr. F. MosK Third Vict-Prttidtra Mr. R. T. C«AWro«D CSludents' Ob«rv»tory, Berkeley) Sicrilart Mr. R. G. AiiKCH (Mount Hamillon, Cal.) Sicrtlary Mr. J. D. Galioway Trtanrtr Board of Dirtclori — AiTKES. Uuickiialteb, Cahpiell, CtAwnuo, CxocxMk, Cl-uhhc, Gallowav. Uax-s, Moue, Kicuabdwh, Town lev. Fi*atict Ci,n.ir.il!ct — Meiiri. CviHlM}, Cioceeb. Aitkeh. Commillrt on Publiralion — Meura. TawHLII, Maddbill. Moobe. Library Commiiict — Mairi. CiAWmiD, Tdwnley. Eiraudh, Car«tl-Mrdal CemmiHtt—Ucnrt. Caufieu. (ex-officio), Pebbine. Towwley. 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V \\ \ 1: ; 1 \, ' ^ - - - — — ---- 1 — - V" — ^ w - — — PUBLICATIONS OF THE Astronomical Society of the Pacific. Vol. XX. San Francisco, California, December 10, 1908. No. 123 A REMARKABLE STAR-STREAM IN TAURUS. By W. W. Campbell, It is well known that many rather widely separated stars possess proper motions, — i. e., motions at right angles to the lines joining the stars and observer. — of essentially the same magnitude and direction ; as, for examples, certain stars in the "Big Dipper/' and the majority of the stars in the Pleiades cluster. In a recent issue of the Astronomical Journal, Professor Boss, of Albany, announced and discussed a most remarkable case of this nature, embracing about forty stars of magnitudes 3^2 to 7, in the constellation Taurus. Certain of the stars near the center of the group engaged Professor Boss's atten- tion as long as twenty-five years ago, in that their proper motions were seen to be nearly identical. The recent comple- tion of his "Preliminary General Catalogue" of the positions and proper motions of the brighter stars enabled him to recog- nize thirty-nine, and possibly forty-one, stars whose direction^ of motion converge to a common but distant point, and whose speeds are such that they will apparently arrive in the vicinity of the converging point simultaneously. The accompanying illustration expresses the main facts more forcibly than words can do. The present positions of the stars are given by the round dots, and their speeds and directions of motion are indicated by the arrows drawn from the dots. It will be seen that these stars form a widely extended cluster, about 15° in diameter,^ with marked central condensation; * The right ascensions, extending from 3h 44m to 6V\ %to, ate ^Wttv «\otv% ^t \*iV- toio 0/ the chart, and the declinations. -»- 5° to +23°, a\ouf^ 1\\« T\i,Vv\ e^^t. 278 Publications of the that they are all (with two possible exceptions) aiming ap- proximately for the jx)int of convergence at the left edge of the charted region; that those furthest to the right have in general the largest proper motions ; and that with the progress of time the cluster will become more and more condensed. It should not be concluded that the component stars of the scattered cluster are really approaching each other, as their motion toward the converging point seems to suggest. Pro- fessor Boss's discussion leaves essentially no doubt that the stars are moving along parallel lines ; and as these lines extend further and further into space, they appear to unite at the converging point. The lengths of the arrows represent the motions that will occur in the next fifty thousand years. By virtue of the increasing distances of the stars from us, their apparent motions will decrease with time, so a period of sixty- five million years, more or less, will be consumed in traveling to the vicinity of the vanishing point (never actually reaching it), at which time this group would ''appear as a globular cluster about 20' in diameter, and constituted largely of stars of magnitudes 9 to 12, with a well-marked central condensa- tion." The direction of motion is necessarily one of recession from the observer, for the stars arc approaching the vanishing point. The cHrection of motion in space is inclined 27^.5 to the line drawn from the observer through the center of the cluster. Professor Boss notes that the stars in the cluster, moving with equal speeds in parallel lines, should have nearly equal speeds in the lines of the observer's sight : a certain average speed for the stars nearest the center of the cluster : related higher speeds for those nearer the radiant : related lower speeds for those further from the radiant; and, if the speed of any one star in the grouj) be observed by means of the spectrograph, the corresponding si)eeds and parallaxes of all the stars in the cluster may be computed. The spectrographic velocities of three stars in the group have been measured and published by Professor Kustner: — y Tauri -\- 39.6''"^ per second. 8 Tauri -f 40.8 « Tnnri +394 t< i< • 4 ti Astronomical Society of the Pacific. 279 From these Professor Boss has computed the speed of the entire group of stars to be 45.6*^™ per second toward the van- ishing point; and the average parallax of the group to be 0".025. Inasmuch as the extreme outer stars of the group are sepa- rated by 15°, their minimum distance apart must be greater than one fourth (15/57.6) the distance separating us from the group, — that is, the most widely separated stars in the group must have a mutual parallax less than four times o".025, or o".i. Professor Boss reminds us that more than thirty stars of those nearest to our Sun have parallaxes exceeding o".i. The vast space through which these thirty stars are extended has a diameter only twice the minimum diameter of the space in which the stars in the cluster under discussion are distributed. It is difficult to account for the origin of such a widely separated group of stars, traveling with equal speeds along parallel lines. It should be noted that some 15*^™ of the observed speed of recession of the cluster is due to the recession of the solar system away from the cluster. About seventy-five other stars in the same region, brighter than the seventh magnitude, do not have the distinctive proper motions of the cluster, and are consequently not connected with it. Nine of the cluster stars have been observed with the Mills spectrograph of the Lick Observatory, as follows: — Star. y Tauri S Tauri ic Tauri 68 Tauri v^ Tauri e Tauri ff Tauri ff Tauri c Tauri No. of Obs. 6 6 2 3 I 6 4 6 3 Dates. 1897-1908 1899-1907 1904 1905-1908 1904 1898-1906 1905-1908 1903- 1908 1905-1908 Velocities. -f 35.8 to + 40.0 + 38.0 to + 38.8 + 12 to + 44 + 34 to + 36 + 40.6 to + 37-8 + 37 to + 38 + 17 to +80 + 45 to +66 Remarks. Probably variable of long period. Poor spectrum; small weight, perhaps of vari- able velocity. V^cry poor lines. Binary. Measures of i line only. Suspected binary. Six of these stars have velocities in good agreement with the requirements of the cluster theory, and the other three 280 Publications of the stars, two of which have spectra with poorly defined lines, afford no evidence in opposition to this theory. The spectra of twenty-three other stars in the same region of the sky have been observed with the Mills spectrograph, but none of them show speeds in the vicinity of + 38*^"*, with the possible exception of two or three having variable velocities. THE NORTHERN LIMIT OF THE ZODIACAL LIGHT.^ By E. a. Fath. The boundaries of the zodiacal light are hard to determine because of the faintness of the phenomenon, although the light along the axis is quite strong and can be seen even in cities in spite of the electric illumination. From the usual observa- tions of the boundaries of this light we should expect the light to extend about 20° to the north and south of the Sun. That the zodiacal light is of much greater extent is evident from the observations described below. In the summer of 1907 Director Campbkll, of the Lick Observatory, called the writer's attention to a faint light, which for years has been seen in the summer by various observers at Mount Hamilton, extending along our northern horizon near midnight, and asked that an attempt l>e made to determine its character. Observations were accordingly begun and continued during the summer of 1908. The general appearance of the phenomenon when observed near midnight, with a clear sky and no Moon, is that of a flat arch of light with its maximum intensity near the north l)oint of the horizon. At that time of night in the early part of July, 1908, the greatest altitude above the northern hori- zon was 18^. It extended westward about 40° and eastward to the Milky Way, and was symmetrical with respect to the meridian. At the extremities it was only a degree or two above the horizon, depending on the clearness of the air at such a low altitude. When, however, the observations were ' For a complete accounl ste Liilc Obscnalory Bulletin, No. 14:;. Astronomical Society of the Pacific. z8i made before midnight the maximiiin was always to the west of the north point, and after midnight always to the east. Three hypotheses as to the origin of this light in the north seemed to require examination: i. That it is an aurora; 2. That it is twilight ; and, 3. That it is the zodiacal light. These hypotheses will now be examined. The aurora hypothesis is not satisfactory for three reasons: 1st. The light is seen only in the summer, during a period of about two months on either side of the summer solstice. 2nd. Observations made with a spectroscope on several even- ings showed the aurora line, A 5571, to be visible in all parts of the sky, and no brighter when the spectroscope was pointed to the maximum of the luminous area than when pointed many degrees away and entirely outside it. 3rd. Observation shows that the maximum of the light moves with the Sun. If the light were twilight it seems reasonable to suppose that the mean of the observations would show the maximum intensity to be on or very near the vertical circle passing through the Sun. The mean of twenty-nine observations, taken from June 27 to August 27, 1908, places this maximum i°.j farther east along the northern horizon than this vertical circle. Moreover, an observation taken at midnight on July 2d shows that the light could be seen 46° north of the Sun. It has usually been stated that twilight ceases when the Sun is 18° below the horizon. At the time of this observation the Sun was 30° below the horizon, and thus 12° lower than the twilight limit. In order to test the question as to the duration of twilight quite a number of observations were made during the summers of 1907 and 1908. They agree in placing the Sun very close to 18° below the horizon at the close of twilight in the evening or the beginning of dawn in the morning. The twilight hypothesis, therefore, does not explain the phe- nomenon satisfactorily. Of the three hypotheses that of the zodiacal light remains. Observations on seven nights showed a direct connection of this light and the ordinary cone of the zodiacal light, a prac- tically straight line forming the northern boundary of both the cone and the light under observation. During the sum- mer months the zodiacal light can readily be seen at Mount Haniilloii. both in the west in the evening ami in the east't the morning. The connection was seen with both the eastern" and western cones. The i°.y displacement, referred to above, of the i of the hght to the east of the vertical circle passing through the Sun appears significant. If we assume ihe axis of great- est intensity of the zodiacal light to be in or near the ecliptic, then at midnight at the time of the summer solstice the axis will be perpendicular to the vertical circle passing tliroiigii the Sub. Before midnight the western angle between the axis and the vertical circle will be less than 90°, and after midnight the eastern angle will be less. In general, before the summer solstice the western angle will average less throughout the night than the eastern, and i.'ice versa. Now. talcing two points at the same altitude and symmetrically situated with respect to the vertical circle, the one to the west would aver- age nearer the axis throughout the night for observations before the solstice, and therefore be the brighter. In the same way, after the solstice, the eastern one wonld be the brighter. We might expect, therefore, that before the solstice the max- imum observed inten.sity would be shifted toward the west and after the solstice toward the east, the shift varying with the distance of the Sun from the solstice. Now we find an observed displacement of i".? toward the east, and all the observations u|Mn which this observed displacement depends were made after tlie solstice. The observations also show a tendency for the displacement to increase with the time. The observations thns agree with the hypothesis. Another test was then applied. It was found that if the point of greatest altitude was connected with the point of greatest eastern or western extent, and continued until it intersected the ecliptic, these intersections were located from 40° to 105° from the Sun. On plotting the results it was seen that the light was distributed fairly symmetrically with respect to the Sun. It passes 46° to the north and intersects the ecliptic about 70° on either side. This applies, of course. only to the part north of the ecliptic. Assuming symmetry with respect to the ecliptic also we have the lenticular appear- ance of the zodiacal light. The effect of atmospheric absorp- Astronomical Society of the Pacific. 283 tion would be to bring the intersections too ciose to the Sun. The apex of the zodiacal light cone can be seen at various distances from the Sun ranging from 40° to over 100°. This agreement between the observed position of the apex and the position, of the intersections is as satisfactory as can be expected from the nature of the objects observed. The observations were then used in another way. The northern boundary of the cone of the zodiacal light had been located with reference to the stars. This boundary was then located on a celestial globe and extended until it intersected a great circle passing through the Sun and perpendicular to the ecliptic. The mean of fourteen observations of this kind showed that we should expect the zodiacal light to pass 42° north of the .Sun. Observations above the northern horizon give 46°. The writer also examined the observations of Jones,* and found that by extending Jones's boundaries of the zodiacal light they would in many cases exceed latitudes of 45° both north and south of the Sun. From the evidence at hand it seems fair to conclude that the phenomenon observed is the zodiacal light, and that therefore its northern boundary, as seen from the Earth, can be traced 46° north of the Sun, and in consequence the zodiacal light is much greater in extent than has usually been supposed. In conclusion, it should be stated that as early as 1840, Herrick,^ of Yale University, thought he had evidence that he' could sometimes see the zodiacal light along the northern horizon in Connecticut, but he made no observations to test his theory. In 1905 Professor Newcomb^ observed the zodi- acal light to a distance of 35° north of the Sun ; and Professor Barnard* says he has at times seen a faint glow in the sum- mer along the northern horizon at the Yerkes Observatory. So far as the waiter has been able to detemiine these are the only other observations of this nature. Mt. Hamilton, November 6, 1908. * Observations of the Zodiacal Light, Vol. Ill of the Report on the United States Japan Expedition, 1856. * Sillitnan's Journal of Science, 80, 331, 1840. * Astrophysical Journal, *2St, 209, 1905. * Astrophysical Journal, 23, 168, 1906. PuhUcatiom of the PLANETARY FHEXOMENA FOR JANUARY AND FEBRUARY, 1909. Bv Malom-m McNeiu.. Full Moon Feb. 4,i3''J5" Last Quarter. . . " 13, 4 47 ■ New Moon " 20, J 5J . First Quarter.. " 26, 6 49 Full Moon Jan. 6, 6" i Last Quarter... " 14,10 1 New Moon " 2[, 4 ] First Quarter . . " j8, 7 Mercury passed superior conjunction lale in December. 1908, becotning an evening star, and remains an evening star until February mh. It reaches greatest eastern elongation, 18° 27', on January zfith. This is a very small greatest elongation, as it occurs only four days before perihelion, and in addition the planot is in the southern half of its orbit during the early part of January. This combination makes the present east elongation a decidedly poor one for visibility as an evening star. Still, during the last half of Januarj- and for a few days in February the planet remains above the horizon more than an hour after sunset, and for a few days at the end of January nearly an hour and a half after the Sun has set. It may therefore be seen on a clear evening in the western twilight. The conditions for visibility will be much better about the time of the next greatest east elongation, in May. After passing inferior conjunction on Febniary nth it be- comes a morning star, and by the end of the month is well on toward greatest west elongation, and rises more than an hour before smirise. It is in conjunction with Venus on February 19th. Venus is a morning star throughout January and February. but is gradually approaching superior conjunction with the Sun, the distance diminishing from 31° on January ist to 14" on Februar}' 28lh. The planet is also running south of the Sun. These two causes rapidly diminish the interval between the rising of Venus and sunrise from a little over two hours to only about half an hour on Febniary 28th. The planet is also at nearly its maximum distance from the Earth, Astronomical Society of the Pacific. 285 and conse(|Ut-ntIy not much above its minimum brightness. However, it may easily be seen in the morning twilight, ex- cept possibly during the last few days of February. I'enus is in conjunction with Uranus on January 30th, the latter being only 21' south of the former. Mars is also a morning star, rising shortly before 4 o'clock on January ist and shortly after 3 o'clock on February 28th. Its motion among the stars during the two months' period is 42° eastward and 5° southward from Libra through Scorpio and the southern eirtension of Ophiuchtts into Sogiltarius. On January 2tst it passes about 5° north of the first magni- tude red star Aniares, aScorpU. Mars passed its maximum distance from the Earth in the early autumn of 1908. and is now drawing nearer somewhat rapidly, the distance diminish- ing from 196,000,000 miles on Januarj- 1st to 151,000,000 miles on February 28th. In consequence of this its brightness will nearly double, and it will become as conspicuous as a good first-magnitude star: but even at the end of February its brightness wili be less than five per cent of its brightness at opposition next September. Jupiter rises at 10" p.m. on January 1st and just before sunset on Febniary 28th, as it comes to opposition on the morning of February 28th. It moves westward, retrogrades about 5°, and southward 2°, in the constellation Leo, during the two months, toward the first-magnitude star Regulus, aLconis, and at the end of the period is about ii° east and south of the star. Saturn is an evening star throughout the period, setting at about 11" 30™ P.M. on January 1st, and shortly after 8'' p.m. on February 28tb. It is therefore in good position for observa- tion throughout the two months. It moves about 5° east and 2° north among the stars in the constellation Pisces. On January 1st it is about 5° east of the vernal equinox. On January ist, as seen in the telescope, the apparent width of the rings is not quite one tenth of their breadth. During the year this ratio increases to about one quarter, but toward the close of the year it will diminish to about one fifth. Uranus on January 1st is an evening star, setting about half an hour after sunset, and is much too near the Sun for 286 Publications of the Astronomical Society, &c, observation even with a telescope. It passes conjunction with the Sun and becomes a morning star on January 7th. By the end of February it rises about three hours before sunrise. Its conjunction with Venus on January 30th has already been noted. It moves about 3° eastward in the constellation Sagittarius during the two months. Neptune is in opposition with the Sun and rises at sunset on January 5th. It is moving slowly westward in the con- stellation Gemini, and is a few degrees south and west of Castor and Pollux, the brightest stars of the constellation. (SIXTY-FIFTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to Professor Dr. Max Wolf, Heidelberg, Germany, for his discovery of an unexpected comet on January 2, 1908. Committee on the Comet-Medal: W. W. Camprell, C. D. Perrixe. S. D. TOVVNLEY. San Francisco, December 7, 1908. (SIXTY-SIXTH) AWARD OF THE DONOHOE COMET-MEDAL. The Comet-Medal of the Astronomical Society of the Pacific has been awarded to Professor D. W. Morehouse, Drake University, Dcs Moines, Iowa, for his discovery of an unex- pected con-!ct on Sei)tembcr i, 1908. Committee on the Comet-Medal : W. W. Campuei.l, C. D. Perrixe, S. D. Town LEV. San Francisco, DccemlKT 7, 1908. NOTES FROM PACIFIC COAST OBSERVATORIES. The Zeeman Effect in the Sun. In a previous note' I described my first observations of the Zeeman effect in sun-spots. Since that time many new results have been obtained.^ It has been found that when the Nicol is set at such an angle as to transmit the violet component of a doublet in the spectruTU of a spot surrounded by a right- handed vortex, it will transmit the red component in the spectrum of a spot surrounded by a left-handed vortex. In the laboratory the same effect is produced by reversing the current in the magnet, when observing the doublets along the lines of force. Hence the direction of revolution of the elec- trified particles in the vortex appears to determine the [rolarity of the resulting magnetic field, as theory requires. The ob- served polarity indicates that the sun-spot field is produced by the motion of negative corpuscles. The above results are obtained when the spots are near the center of the Sun. As they advance toward the limb it might be expected that the doublets would change to triplets, as is usually the case with doublets observed in the magnetic field. As this does not occur, it is of interest to note that all of the spot doublets hitherto observed in the laboratory, with one exception, have been found by Dr. King to appear as doublets not only when observed parallel to the lines of force, but also at right angles to the hues of force. As a matter of fact, a polariscopic study of these lines, made by Dr. King, shows that they are in reality quadruplets, though the components of each of the lines of the apparent doublets are so close together that they cannot be separated in the sun-spot spectrum. The 288 Publications of the line A 630271, when observed at right angles to the Hnes'S force in the laboratory, is a triplet.' In the spot spectrum it also appears as a triplet. Since many other lines also appear as triplets in the spot spectrum, it is evident that the light of the spot is partly longitudinal and partly transverse. A comparison of the separations of spot doublets with those of the same doublets obser^'ed in the laboratory gives, in the case of four iron lines, a remarkably close agreement for the relative separations. In the case of titanium, and other ele- ments extending through a considerable range of level in the Sun, there are greater divergences, probably due to the rapid change in the strength of the field in passing upward through the spot. The D and b lines in the spot spectrum, which represent comparatively high levels, show but little effect of a magnetic field. I fence at the distance of the Earth the spot- field would be quite inappreciable, even with very delicate instruments. The strength of the field in spots, at the level represented by the iron doublets, is about 2900 gausses.- It seems possible that the Sun itself, on account of its axial rotation, may also have a magnetic field. The polar rays of the corona, which resemble the lines of force in a magnetic field, long ago suggested this idea to several astronomers. I have accordingly photographed the sixrctrum of points near the Sun's pole through a Nicol (used with a rhomb) set at various angles. Some of the lines which are double or triple in the spot spectrum appear to undergo slight displacements, with reference to telluric lines, when the Kicol is rotated. I am now endeavoring to detennine whether these shifts can be nf instru- mental origin. If not, they may be produced by the Sun's field. George E. Hale. Mt. Wilson Solan Observatorv, December, 1908. ^^M " Double-Star Astkonomy." ^H In No. 120 of these Publicalions I called attention to a series of papers with the title "Double-Star Astronomy," that were appearing in the Obscrvalory. Mr. Lewis has now Astronomical Society of the Pacific. 289 reprinted this series iincier the same title in a handy pamphlet' of forty-six pages, which forms an excellent introduction to the study of double stars. It contains a brief history of the subject, short notices of all the more important double-star observers and publications, the formulae and examples for two methods of computing an orbit, and some miscellaneous formula that are of value. Of s]X!cial interest to the present writer are the sections on the separating power of telescopes, on the application of photography to double-star work, and on personal equation. The last-named topic is one on which considerable difference of opinion exists, and some will undoubtedly disagree with the author's conclusions, though I consider them sound doctrine. As Mr. Lewis's book will be widely read it seems worth while to correct one statement. On page 23 it is stated. "AiTKEN and Hi;ssEy rarely keep a pair separated over 6"." The numeral should be 5". Out of 3.237 new pairs so far published only twenty-five have measured distances exceeding 5".oo. and thirteen of these do not exceed 5". 25. Only two pairs (Hu 738, 6". 50, magnitudes 6.3 — 11.5; and Hu 748, 6". 04. magnitudes 6.2 — 12.8} exceed 6" .00. This statement, of course, applies to the closer pair of the system. Occasionally measures are given of one or more additional stars at greater distances. Another publication of interest to double-star observers is Professor Lohse's paper. "Doppel Sterne,"' published by the Potsdam Observatory. In addition to a good series of meas- ures of selected pairs made with the ii-inch refractor, Pro- fessor LoHSE gives the results of his investigations of the motion in thirty-two systems. In a few instances he concludes that no improvement can be made upon existing orbits, but in most instances he computes a new orbit by graphical meth- ods, which in a number of cases he corrects by a least -stju ares solution. It happens that I have later measures of twenty-two of the stars investigated, and I have been interested to see how nearly my measures are represented by the new orbits. In eleven pairs, the residuals are within the limit of error hy T. Lewis. Sec. K. 290 Publications of the of observation, in five others (including ^8648, of which there is no other orbit) they are fairiy satisfactory, but in the remaining six (jS 524, ^8883, 02 235, (Scorpii, ^8416, and 85 Pcgasi) the residuals in angle average over 23°, and one of the distance residuals, in )8 4i6, exceeds o".4. November, 1908. R- G. AlTKEN. Note on the Binary Star $ScoRPir. Two orbits for this well-known binary system have recently been published, one by Doberck^ and one by Louse.- Both are based on practically the same data as my orbit published in 1905,^ and both computers have adopted the assumption made by me, that the periodic time is about 44.5 years instead of over one hundred years. The three sets of elements do not differ greatly, but the motion in the apparent orbit has been so rapid during the past three years that even slight variations in the elements lead to decided changes in the residuals derived by comparing the computed and observed positions. The following tabulation gives my measures made after my orbit was published, and the residuals derived by com- j)ariny; them with the three sets of elements : — Po Nights. (() D A. o".i8 3 — 5°-6 4-o".02 o .23 4 — 13 .3 -}-o .02 o .32 4 — 9 .4 +0 .01 o .36 2 — 10 .4 — o .06 These residuals put the correctness of the short period of revolution beyond question, and indicate that the other ele- ments of the orbit are fairly well determined. Further com- putation will not be profitable until the companion star has passed nearly throuj^h the second quadrant. November, 1908. ^- ^- AlTKEN. ^ . lsir(>iu)n:i.<:iiit' \achri,litcn, 174, ^57, 1907. • I'uh. ,/. .Istrcf-liyxik. Ohscrv. zu Potsry Bulletin, No. 107. 1905. Date. f'o 1905.50 13° .8 1 906. 38 68 •7 1907.40 108 2 1908.48 1^5 .8 (O c» n. (O-O L. — 19°. I -|-o".o3 i4°.8 -^ o".c — 25 .6 -f- 0 .03 — 29 .6 -^. 0 .c — 17 .4 -|- 0 .01 — 21 .3 — 0 .c — 15 .6 — 0 .07 18 .8 0 .1 Astronomical Society of the Pacific. 291 A New Binary Star. The bright star 46 Tauri (R. A. 4»» 8™ iC, Decl. + 7° 28', 5.3 magnitude) was found to be an unusually close double star when examined with the 36-inch telescope on November 18, 1908. The mean of two nights' measures is: — 1908.90 3iS°.4 o".i4, 5.7-6.2 magnitudes. On the first night the telescope was west of pier, on the sec- ond night east, and the two angle measures agree within 0^.3, the distance measure on each night being o'^I4. As the star is assigned the proper motion of — o'.oo20 and + o'^023 in R. A. and Decl. respectively, or 0^^.038 in the direction 307^.7, it is obvious that this is a physical system ; otherwise it would have been discovered long ago. Another pair, equally dose but fainter, discovered on the same night, is A. G. Berlin B 455 (R. A. i^ 24"^ 13", Decl. -|- 22° 19% magnitude 6.5). The chances are hundreds to one that it also is a binary system, though the star catalogues do not assign it any proper motion. Measures on two nights give : — 1908.90 126^.2 o''.i4, 6.7-7.2 magnitudes. The two angle measures, made on opposite sides of the meridian, agree, within 0^.9, and the distances within o'^OI. November, 1908. R- G. AlTKEN. The Carnegie Institution Observing Station in the Southern Hemisphere. ^ Director Lewis Boss, of the Dudley Observatory, Albany, and Astronomer Tucker, of the Lick Observatory, sailed from New York last August to Argentina to establish the observing station referred to in the title. The instnmiental equipment is to consist chiefly of the Dudley Observatory meridian circle, and the purpose is to observe the accurate positions of all bright stars down to the seventh magnitude, in order to sup- plement Professor Bosses exactly similar work at Albany, thus making his programme cover the entire sky. The observations to be secured will be utilized in combination and comparison with all similar observations of the same stars made in earlier 292 Publications of the years, to determine the positions and the proper motions of the stars. This plan, embracing every star in the entire sky down to the seventh magnitude, is one of the most extensive and ambitious recorded in the history of astronomy ; and there is full confidence that the results will be correspondingly valuable. The site for the observing station was fixed at a point about a kilometer from the center of the citv of San Luis, in the west-central part of Argentina. Professor Boss has written that the government officials and the people have been most sympathetic with his aims. The site was provided by the National Goverimient on national property, and in many other ways definite assistance was afforded. Building operations were well under way within two weeks after the astron- omers landed in Buenos Aires. Professor Tucker will be astronomer in charge of the observing station during the three years of work planned for. He will have a large corps of assistants in order that the instrument may be kept busy and the calculations be made promptly. Albany newspapers report that the ship on which Professor Boss took homeward passage was wrecked shortly after leav- ing Buenos Aires, and if the reports are trustworthy there must have been cause for great anxiety for a day or two. \V. \V. Campbell. PlIOTOr.KAPHIC DeFIXITION FROM LiGHT OF DIFFERENT Wave-Lexgths. The lari^e size of the photographic images of stars obtained ' with telcsc()]K^s of sixty to seventy feet focal length, has led the writer lo look for means of reducini^: them. Without goiipj: into the matter of "seeing" deeply, it may be said that, in all probability, the character of the images depends almost wholly Uj)on atmospheric refraction. Assum- ing this to he the case, star images, for example, formed by vellow liirht should be much less affected bv disturbances of the atmos])licre, and consequently l)e smaller than images formed by light of the short wave-lengths (blue and violet), which affect the ordinary photographic plate most. Astronomical Society of the Pacific. 293 Photographs taken with the new 70-foot combination of the Crossley reflector, in the ordinar}' bhie and violet Hght, and also on orthochromatic plates, using a greenish-yellow color screen, show that the star images which have been formed by yellow light are much smaller than those formed by the ordinary blue and violet light. Similarly, photographs of the Moon and planets are sharper in yellow than in blue light. Extension of this reasoning points to the deep red part of the spectnun as being favorable for the production of still smaller images and better definition. In photographic work on bright objects, such as the Sun, Moon, and the brighter stars and planets, the use of light of great wave-length is entirely practicable. A consideration of visual definition seems to point to an analogous eflFect there, although to a less degree, owing to the greater wave-lengths to which the eye is most sensitive. A detailed account of the experiments already concluded, as well as some still in progress, will l>e published shortly in a Lick Ohsen-atory Bulletin, q D. Perrine. Mt. Hamilton, Cal., December 5. 1908. Eighteen Stars Whose Radial Velocities Vary. In the progress of the work with the three-prism Mills spectrograph at Mt. Hamilton, and of the D. O. Mills Expedi- tion to the southern hemisphere, eighteen stars have recently been found to have radial velocities which vary, on account of the gravitational influence of an invisible but massive com- panion in each system, except that in case of one star, 70 Ophiuchi, a well-known visual double star, the companion is visible. A list of these stars, with data concerning their positions, number of observations, total range of observed velocities, and discoverers of the variations, is given below. Only in the case of 70 Ophiuchi is the revolution period known, — in that case eighty-eight years. Detailed data con- cerning the observations are contained in a Lick Observatory Bulletin now in press. 294 Publications of the Astronomical Society, &c. Ncoi Star. R. A. Dec. lype. Observed in. Obs. Velocity. Discoverer y Persei 2^ ' 57"^.6 + 53' ' / G 1897 to 1908 II — 2tO-|- 7*^™ Moore. ^ Tauri 3 21 .8 + 9 23 A 1903 to 1908 5 — 62 to -f 36 Campbell. $2 Tauri 4 22 .9 + 15 39 A 1903 to 1908 6 -f 17 to 4-74 Moose. / Eridani 4 33 .6 — M 30 I 1900 to 1908 6 ■4- 33 to -H 43 MOOKE. ^AurigcF 4 55 -5 4-40 56 K 1898 to 1908 7 ± oto 4-25 WSIGHT. p Ononis 5 8 .1 -f 2 45 I 1902 to 1908 6 + 33 to -h 50 MOOIE. ^Can. Maj. 6 16 .5 — 30 2 B 1906 to 1907 12 + 11 to + 38 Paddock. pCan.Maj. 6 18 .3 — 17 54 B 1904 to 1908 + 27 to + 41 .\lbsecht. y Puppis 6 34 .7 — 43 6 B 1904 to 1908 8 + 20to + 35 Wright. rPuppis 6 47 .4 — 50 30 K 1903 to 1907 6 + 30.4 +40 Curtis. 0 Velorum 8 37 .4 — 52 34 B 1904 to 1908 II + 10 to + 27 Curtis. d Caritm 8 38 .5 — 59 24 B 1907 6 + 38to + 72 q Velorum 10 10 .6 — 41 37 A 1904 to 1907 4 — 2 to -{-25 Paddock. y' Draco tt is 17 30 .3 + 55 14 A 1902 to 1908 — 23 to— 4 Albrecht. 70 Ophiuchi 18 0 .4 4- 2 32 K 1897 to 1908 8 — 10 to— 7 III Her cults 18 42 .6 + 18 4 A 1902 to 1908 6 — 26 to — 64 Wright. <^ CygMt 19 35 .5 + 29 56 I 1907 to 1908 '■{ It oto — 24 ) It 0 to -f 30 j Plumwer. Campbllu yOctantis 21 30 .4 — 77 50 K 1904 to 1907 '8 + 27 to -f 36 W. W. Ca Wright. * Two components visible. MPBELL. December 7, 1908. AprOIXTMENTS. Mr. E. A. I'\\Tii, r>llow in the Lick Observatory, has been appointed Assistant in the Solar Observatory of the Carnegie Institution, dating from July i, kjck). ^y -^y rv^^ipBFiL Director W. W. CAMPiiiiLL, of the Lick Observatory, has been invited to give the Silliinan Lectures in Vale University for the academic year 1909-1910. The course will consist of ten lectures, dealing with the results of Professor Campbell's work in measuring the radial velocities of stars by means of the spectroscoi)e and the solution of several fundamental prob- lems of astronomy as based upon these motions. The lectures will probably be given in the fall of 1909. j it ^jqq«p GENERAL NOTES. The Parallax and Proper Motion of the Double Star Krucger 60, — The double star known as Krueger 60 is of un- usual interest for several reasons. It is a faint star, the B. D. magnitude being only g.o, and so wide that no appreciable relative motion of its three components was to be expected within a century. The first accurate measures were made by Bl'hnham — who in fact discovered the closer pair — in 1890, and when his resiUts were compared with those of Doolittle, the next observer, in 1898, it was found that the distance of the wide pair had increased from 26".8 to 34". 4, while the close pair showed a decrease in position -angle of nearly 40° with increase of distance of nearly o".9. It therefore appeared probable that the close pair was a binary in rapid motion, and that it had a strong proper motion as well. The combination of rapid orbital motion, strong proper motion, and large apparent angular separation indicated that the pair, in spite of its faintness, was one of our near neighbors in space, and observations for parallax were accordingly instituted at the Yerkes Observatory, both visually, by Earn.ard. and photo- graphically, by SciiLESiNGEB. The latter's preliminary results were published in the Aslrophysica! Journal for September. 1904. They ranged from -f o".226 to +o".30i, the mean being about o".25. Professor Barnard's very complete discussion has now been published in the Monthly Notices R. A. S. (Vol. LXVIII. No, 9). The determination of parallax and proper motion of A rests upon his observations with the 40-inch telescope of the wide pair A C made in the years 1900 to 1905. inclusive. The solution of the seventy-six equations of condition gives the value t- — -f- o.",249 ± o".oi05. For comparison, Dr. Schlesinceb's final results' are given, and also, in a post- script, Dr. H. N. Russell's value obtained from photographs with the Cambridge (England) refractors. Yerku 01«*t^ • 296 Publications of the The three values are: — SCHLESINGER + 0''.248 zh O^'.OOQ Barnard +0 249 zL o .010 Russell +0 .258 dt o .013 The excellent agreement of these independent determinations is the best possible evidence of their accuracy. We may there- fore assert with confidence that Krueger 60 is our close celes- tial neighbor, light requiring only a little over thirteen years for its journey across the intervening space. For the proper motion, Barnard gives the value o".968 in 246°. 49. He adds an interesting discussion of the irregularity of the proper motion of the star A, due probably to its orbital motion about the center of gravity of the pair A B ; also, all his micrometer measures to date, including those of some more distant stars. The angular motion of the close pair in the eighteen years since its discovery has amounted to 74°. The apparent distance seems to have reached its maximum value about the year 1904, and is now diminishing. It may therefore be possible to form some estimate of the periodic time before many years. r_ G. A. Tcmpcl^-Szi'ift Comet. — On September 291)1, M. Javelle, at Nice, rediscovered the Tenipel^^-Swift comet. Its observed position differed over 15™ in Right Ascension and nearly 1^.5 in Declination from the computed position according to ^Iau- baut's ephemeris. Perihelion passage occurred on September 30th. This comet was discovered by Tempel in 1869, and when rediscovered bv Swift in 1880 was found to move in an ellipse with a period of five and one-half years. The comet was not found at its return in 1874. nor at any of the returns since 1880, except in 1891, when it was rediscovered by Barnard. Xotcs from ''Science.^' — Dr. S. Tschernv, of Kiev, has been appointed director of the university observatory in Warsaw. The Astronomical and Astrophysical Society of America will hold its next meeting in the summer of 1909, probably at the Yerkes Observatory. The exact date has not yet been Astronomical Society of the Pacific. 297 fixed, but it is expected to precede by a few days the Winne- peg meeting of the British Association for the Advancement of Science, which will open on August 25, 1909. Mr. Andrew Graham, from 1864 to 1903 first assistant at the Cambridge Observatory, known especially for his work on the Cambridge star catalogue published in 1897, ^i^^ recently at the age of ninety-three years. We regret also to record the deaths of Dr. John M. Thome, director of the Cordova Observatory since the retirement of Dr. Gould; and of Mr. Archibald J. Little, who did valuable geographical work in the interior of Asia. In the November Astrophysical Journal, Messrs. A. Fowler and A. Eagle, of the Imperial College of Science and Tech- nology of London, show that a spectrum of linear dispersion on any reasonable scale can be obtained photographically from a prismatic spectnun plate by setting the two plates at proper distances from the lens and tilting them at definite angles. Formulae are given. An example shows the remarkable accu- racy obtained with ordinary apparatus. TDM Cecil Goodrich Dolmage. — The following clipping from the London Times announces the death of Dr. C. G. Dolmage, a member of the Astronomical Society of the Pacific since 1899: — "The death of Dr. Cecil G. Dolmage, author of 'Astronomy of To- day,* a work which has been widely praised, has come as a sad blow to his numerous friends in Dublin and in London, where he had resided for some years past. He took high honors at Trinity College, Dublin, in modern history in 1893, and, devoting himself to intellectual pursuits, accomplished for astronomy, his favorite study, much useful work by his wide knowledge and facile pen. Some eighteen months ago, when on a trip to Italy, he fell dangerously ill ; and, though hopes of recovery were entertained, he fell into a steady decline. He was a Fellow of the Royal Astronomical Society and many other learned societies at home and abroad. A man of a singularly truthful and upright nature, of modest manner, and of noble mind, his death will be mourned by many men of varied types whom his ability and personality attracted to him." NEW PUBLICATIONS. Annales de TObservatoire Astronomique de Z6-se (Chine). Tome II. Annee 1906. Chang-Hai, 1908. 4to. 62 pp. Seven plates. Paper. Atlas Stella rum Variabilium. Series sexta. Composita a I. G. Hagen, S. I. Berolini. 1908. Folio. Cloth. Beitrag zur Bestimmung der Konstanten der Physischen Libra- tion des Mondes. II. Reihe der Heliometrischen Mes- sungen in Kasan. Ausgefiihrt von A. Michailowski. Bearbeitet von Dr. Max Volkel. Kasan. 1908. 4to. 46 pp. Paper. Brown, Ernest W. The inequalities in the motion of the Moon due to the direct action of the planets. Cambridge. 1908. 4to. xii + 92 pp. Cloth. Goos. Fritz. Der Spektroskopische Doppelstern Capella. Inaugural Dissertation. Bonn. 1908. 4to. 50 pp. Paper. HiRAYAMA, K. Declinations and i)roper motions of 246 stars. Annales de TObservatoirc Astronomique de Tokyo. Tome IV, I fascicule. Tokyo. 1907. 4to. 195 pp. Paper. LuDENDORFF, H. Dcr Vcranderliche Stem R Corouae Bore- alis. Publikationcn des Astrophysikalischen Observ^ato- riums zu Potsdam. Potsdam. 1908. 4to. 61 pp. Mit 7 Tafeln. Paper. Morrison, Hugh Alexander. Preliminary check list of American almanacs 1639- 1800. Library of Congress, Washington. 1907. 4to. 159 pp. Cloth. NicoLis, I'go. Sul cerchio meridiano delTOsservatorio de Modena. Pubblicazioni del r. Osservatorio Geofisico di Modena. Modena. 1907. Folio. 13 pp. Paper. PuiSRL'X, P. La terre et la lune forme exterieure et structure interne. Paris. 1908. 8vo. 176 pp. 51 figures. Paper. Publications of the Astronomical Society, &c. 299 Royal Observatory. Results of the astronomical observations made at the Royal Observatory, Greenwich, in the year 1906. Edinburgh. 1908. Folio, cxliv + 1 16 + 92 + 180 pp. Boards. Solar Physics Committee. On the general spectra of certain type stars and the spectra of several of the brighter stars in the green region. London. 1908. 4to. 46 pp. One plate. Boards. Wyman and Sons. Price, 3s. 300 Publications of the Minutes of a Special Meeting of the Board of Directors OF the Astronomical Society of the Pacific. Held IN Rcx)M 6oi Merchants Exchange Building, San Francisco, Monday, October 12, 1908. The meeting was called to order at 4:30 p.m. by President Burck- HALTER. The following directors were present: Aitken, Burckhalter, Camphell, Crawford, Gushing, Galloway, Morse, Richardson, TOWNLEY. Moved and seconded that the action of the President and Secretary in sending requests for nominations for the award of the Bruce Medal for 1909 be approved. Garried. The following were elected to membership : — Mr. G. T. Webster Box 782, Globe, Arizona. Mr. Edwin G. Benkm AN. .2267 Turk Street, San Francisco. Mr. Edwin I. Barnes R. F. D. No. i, Chanute, Kansas. Mr. John A, Langstroth . Perry Street and Grand Avenue, Oakland. Moved and seconded that the matter of revising the By-Laws pre- paratory to their re-publication be referred to the Committee on Publication, to report at the next meeting. Carried. Mr. Gushing made an oral report on the proposition of moving the library to San Francisco. No action was taken. The resignation of Mr. Galloway from the position of Treasurer was presented. Upon motion, duly seconded, the resignation was ac- cepted, to take effect upon the qualihcation of his successor. Moved and seconded that the Secretary cast the ballot for the elec- tion of Mr. Richardson to the position of Treasurer. Carried. The ballot was cast and Mr. Richardson declared elected. Moved and seconded that, beginning with the month of October, the salary of the Treasurer be fixed at $io per month, and that the salary of the Secretary be fixed at $10 per month. Carried. Moved and seconded that the President and Chairman of the Finance Committee be authorized to compromise with the Rhine-Moselle Fire Insurance Company at the best terms obtainable. Carried. Adjourned. M1NUTE.S OF tiik Mektixg of the Board of Directors, Held IN Room 601 Merchants Exchange Building, San Francisco, Cal., November 28, 1908, at 2 o'clock p.m. President Burckhaltkr presided. The following directors were present: Burckhalter, Crawford, Cushing, Gallow.w, Morse, Rich- ardson, Town LEV. Moved and seconded that the President appoint a permanent medal committee of two; this committee to have charge of all matters con- Astronomical Society of the Pacific. 301 cerning the procuring of medals. Carried. The President appointed the following committee: F. R. Ziel (chairman), R. T. Crawford. The Secretary reported the receipt of an appreciative letter from Mr. John Grigg acknowledging the receipt of the comet medal that had been awarded to him. Moved and seconded that the Treasurer be authorized to secure a safe deposit box at the Crocker National Bank; the rental to be $4.00 per annum. Carried. Moved and seconded that, according to the By-Laws, the Treasurer give a bond in the sum of $500, furnished by two individual sureties, or one security company; the bond to be approved by the President. Carried. Chairman Cushing, of the Committee on Location, made a verbal report. Moved and seconded that the January meeting of the Society be held at the Chabot Observatory. Carried. By ballot, the eighth award of the Bruce Medal, for the year 1909, was made. The name of the recipient is not to be made public until after January i, 1909. Adjourned. Minutes of the Meeting of the Astronomical Society OF THE Pacific, Held at the Students* Observa- tory, Berkeley, Cal., November 28, 1908, AT 8 o'clock p.m. The meeting was called to order by President Burckhalter. Moved and seconded that the minutes of the last meeting, as pub- lished in the Publications, be approved. Carried. There being no further business, the President introduced Dr. Joseph H. Moore, of the Lick Observatory, who delivered a lecture upon "Variable Stars." At the conclusion of this lecture Dr. Sidney D. TowNLEY, of Stanford University, was introduced and gave a lecture on "Variation of Latitude." Both lectures were illustrated with stereopticon views. Adjourned. 302 Publication! of the Astronomical Society, OFFICERS OF THS SOCtSTV. Mr. CUAKUI DlJ«CKHM.IM F Mr. W. W. CAMfBiu. Firil yict-FrtiUnt Mr. G. E. Hali Sttond yUt^rttUnt Mr. F. MoilE Tkirrf yict-Prtndnt Mt. R. T. CiAWfoiD (SludenW Otaerysloty, Derkeley) S*cr*ttr Mr. R. G, AiTmw (Mount Hioiiltini, OL) SurHarj Mr. n. S. KiCMAUDSOli Trtaiurtr Beard of Dirieto't — Aitkin, Bu*ckiiu.tei, Cauthli, Ckkwrou. Cu>ck», Ci-tuiHC, Calu>way. Hue. Mote, Ricbakdwh, Towmliv. Fjiuiin Ceri'tKillft — Meun. CitaHtHo, Ciockei. Aituh. ^^m CommitUi 0H ^HftliralJon — M«ari. TowKLtv. Mawxill, Uoovs. ^^H Library CommiUct — Meura. Cuwidhd. Towhlev. Eihauoh. ^^| CDmrLlfrifil CommiUfc—tiettn. Cuifbeu. (ucoffifiD), Puiihi. Towhut. ^^I NOTICE. Article Vlll of ibc Uy-Laws oi tbe Society, u >nicR<]fd in igoj. reads u Eollawi: "Each active member ihall pay. aa aaaual dun, the lum of hve daUati, due on the first day of January of each year in advance. When a new mcabu ii elected during the first quarter of any year, he ahall pay full dun far tucli yeac; when elected during [be aecond quaner. be shall pay ibree foanht only of of lucb duo; when elected during the last quarter,' be shall pay one fourth only of luch dues; provided, however, that one half only of the dues in Ihis aniele learniiiM. during such time >s he is » enrolled. . . . Any memlicr may be released from annual dues by the payment of fifty dollars at any one lime, and Volumes for past years will be lupplied to members, so far as Ihe stock on hand is sulEcienl. on the payment of l»o dollars per volume to either of the Secreuries. Sinite copici will be supplied on the following basil; one dollar la non-members, seventy-tive cents to dealer,, and fifty cenls lo membera. Members within the United Slates may obuin books from Ihe library of Ihe Society by sending to the Secretary at Berkeley ten ceiils |>astae< for each book The order in which papers are i-rinted in tbe PublicatiBiu ia decided aimply by convenience. In general ihose papers are printed firai which are earlteal accepted for publicalion. Papers intended to be primed in a given number of the PHblicaluiHt should be in the hands of the Committee not later than Ihe loth of the menlb preceding the month of publicalion. The responsibility for the views eKpreased in the papers printed, and for Ihe form of their expression, rests with Ihe writers, and is not assumed by tbe Society. Articles for the PuUitaticmi ■hould be sent to Ihe chairman of the Committee on Publication, S. D. TowHLir. Stanford University, California. The Secreury al Beikeley will send to any member of Ihe Society saitable stationery, stamped wiih Ihe seal of Ihe Society, al coat price as follow*; a block of letter paper. 40 cents: of nule paper, a; cents: a package of envelopet, 1% cents. These prices include poslage. Regular meetings of Ihe Society are held in San FrsnFisea et vicinity on Ihe last Saturdays of fanuaiT, March, and November, and at the Lick Observatory on Ihe last Saturdays of June and August. Members who propose lo attend the meelings at Mount Ilamillon should communicale with the SecreUry a PUBLICATIONS ISSUED BIMONTHLY. iFfbraary. April, Junt. Atiguil. Ocl^her, Dtrinbir. "ublishcd by the Astronomical Society of the PacifiF at 601 Met dins. San Francisco, California. SuhscripliDn price. 55. ao r INDEX TO VOLUME XX. PAGE. Abbot, C. G., A Bolometric Study of the Solar Corona ... 86 Adams, Walter S. (with George E. Hale), A Comparative Study of the Spectra of the Limb and Center of the Sun . . . 27 Address of the Retiring President of the Society in Awarding the Bruce Medal to Edward C. Pickering, by Charles S. Gushing 55 AiTKEN, R. G., Observations of Saturn's Rings in 1907, 37 ; Recent Double-Star Literature, 181; Measures of /3 2o8, 185; Note on the Orbit of /3 612, 267 ; "Double-Star Astronomy," 288 ; Note on the Binary Star ^ Scorpii, 290 ; A New Binary Star, 291 ; The Parallax and Proper Motion of the Double Star Krucger 60 . . 295 Albrecht, S., On the Reseau, 94; The Coronal Spectrum as Ob- served at the Flint Island Eclipse (with W. W. Campbell), 168; A Disturbed Region in the Corona of January 3, 1908 (with W. W. Campbell) 230 Allegheny Observatory 42, 197 Al^en, Richard Hinckley, Notice of Death of 121 Astronomer's Work, The Nature of an, by W. W. Campbell . 251 Astronomical Observations in 1907, by Torvald Kohl ... 21 Astronomical Society of the Pacific: Annual Meeting of the, with Treasurer's Report, etc. . . 127 Award, Seventh, of the Bruce Medal 26, 52 Awards of the Donohoe Comet- Medal of the 93, 286 Bruce Medalists of the i Corresponding Institutions of the 10 Exchanges of the 12 List of Members of the i Minutes of the Meetings of the 53, 126, 241, 301 Minutes of Meetings of the Board of Directors of the . 5-2, 125, 130, 249, 300 Officers of the 54, 132, 202, 250, 275, 302 Patrons of the i Report of the Donohoe Comet- Medal Committee for 1907 126 Atmospheric Absorption 120 Campbell, W. W., The Eclipse of January 3, 1908, ss; The Crocker Eclipse Expedition of 1908 from the Lick Observa- tory. University of California, 63; The Coronal Spectrum as Observed at the Flint Island Eclipse (with Sebastian Al- brecht), 168; Explanation and Correction, 185; Report of the Lick Observatory for 1907, 186; A Disturbed Region in the Corona of January 3, 1908 (with S. Albrecht), 230; Flint Island Corona, 232; The Partial Solar Eclipse of June 28, 304 Publications of the PACE. 1908, 232; Personals, 240; The Nature of an Astronomer's Work, 251; A Remarkable Star-Stream in Taurus, 277; The Carnegie Institution Obser\'ing Station in the Southern Hemisphere, 291 ; Eighteen Stars Whose Radial Velocities Vary 293 Carnegie Institution Observing Station in the Southern Hemi- sphere, The, by W. W. Campbell 291 Chamberhn Observatory, Report of, 1907, by H. A. Howe . . 98 Coelostat (Vertical), or "Tower" Telescope of the Mt. Wilson Solar Observatory, Some Tests of the, by George E. Hale . 35 Comet c 1908, Note on, by Sturla Einarsson and W. F. Meyer 266 Comet-Orbits, Tables of the Elements of, January, 1896, to De- cember, 1907, by J. C. Duncan 172 Comets, Periodic, Due in 1908 44 Comet- Medal, Awards of the Donohoe 93, 286 Corona, Solar, A Bolometric Study of the, by C. G. Abbot 86 Corona of January 3. 1908, A Disturbed Region in the, by W. W. CAMPBr.LL and S. Albrecht 230 Corona, Flint Island, by W. W. Campbell 232 Coronal Spectrum, The, as Observed at the Flint Island Eclipse, by W. W. Campbell and Sebastian Albrecht .... 168 Crawford, R. T., The Orbit of the Eighth Satellite of Jupiter (with W. F. Meyer) 266 CuRTLS, Hebf.r D., Methods of Determining the Orbits of Spectro- scopic Binaries 133 Dor.l)lc Star^ : Mcasuro nf /i 208. \)y R. G. Aitken 185 Recent l)oul)le-Star Literature. ])y R. G. Aitken 181 Xote on ilie Orbit of ^612, l)y R. G. Aitken 2(')7 "Double-Star Astronomy." l)y R. G. Aitkkn 288 Xoie on tin- P.inary Star ^Scarfyit, by R. G. Aitken .... 290 A New liinary Star, ])y R. G. Aitkkn --91 The r\irallax and Proper Motion of the Double Star Kruc^cr (yo, by R. G. Aitkkn 295 Drifts of Stars uo Di N( AN, J. C Tables of tlie Elements of Comet-Orbits, January, iS*/), to December, 1907 172 Eakl of Rossk, Tlie. Xi»ticc of Death of 2/2 Eclipse. The, of January 3, 1908, by W. \V. Campbell .... t^^ Eclipse. The Partial Solar, of June 28. 1908, by W. W. Campbell 21^'^ Eclipse of the Sun June 28, 1908, OI)servations of the Partial, by C. D. Pkrkink 2;^j^ T'lclipse Expedition, The Crocker, of i(X>8. from the Lick Observa- tory, University of California, by W. W. Campbfjx ... 63 Eclipses and Transits of the Satellites of Saturn Occurring in the Year 1908. by Hermann Stri've 156 Astronomical Society of the Pacific. 305 PAGE. EiNARSSON, Stlrla (with W. F. Meyer), Note on Comet c 1908 . 266 Eros Solar Parallax Work, Progress on the Crossley, by C. D. Perrine 184 Eros, Variation of Brightness (note), by J. D. M 244 Path, E. A., A New Photographic Plate, 239; The Northern Limit of the Zodiacal Light 280 General Notes 41, 120, 196, 241, 269, 295 Greenwich, Royal Observatory 245 Hale, George E., A Comparative Study of the Spectra of the Limb and Center of the Sun (with Walter S. Adams), 27; Some Tests of the Vertical Ccelostat or "Tower" Telescope of the Mt. Wilson Solar Observatory, 35 ; Report of the Solar Observatory of the Carnegie Institution of Washington, Mt. Wilson, California, 1907, 107; Solar Vortices, 203; Solar Vor- tices and the Zeeman Effect, 220; The Zeeman Effect in the Sun 287 Howe, H. A., Report of the Chamberlin Observatory .... 98 Illumination, Field 121 International Latitude Observatory, Ukiah, Report of, 1907, by J. D. Maddrill 98 Jupiter, The Orbit of the Eighth Satellite of, by R. T. Crawford and W. F. Mkver 266 Jupiter, Recent Observations of the Moving Object Near, Dis- covered at Greenwich by Mr. J. Mei.otte, by C D. Perrine . 184 Kelvin, Lord, by H. C. Plummer 13 Kohl, Torvald. Astronomical Observations in 1907 21 Latitude, The Variation of, by J. D. ^Iaddrill 2Cq Lectures at Berkeley, by A. O. Leuschner 97 Leuschner, a. O., Lectures at Berkeley, 97; Report of the Stu- dents' Observatory, Berkeley Astronomical Department, Uni- versity of California 116 Lick Observatory: Report of, 1907, by W. W. Campbell 186 The Difference in Longitude between, and Mare Island Observ- atory, by R. F. Sanford 238 Longitude, the Difference of, between Lick Observatory and Mare Island Observatory, by R. F. Sanford 238 Lowell Observatory, Report of, 1907, by Percival Lowell . . 99 Lowell, Percival, Report of Lowell Observatory, 1907 ... 99 Maddrill, James D., Report of International Latitude Observa- tory, Ukiah, 1907, 98; Achilles Group of Asteroids, 243: Variation of Brightness of Eros, 244: The Variation of Lati- tude 269 McNeill, Malcolm, Planetary Phenomena . 23.91,178.224,261, 284 Mercury, Notes on the Transit of, 1907, November 14th, from Continental Observations 44 3o6 Publications of the PAGE. Meteorites 44 Meyer, W. F., The Orbit of the Eighth Satellite of Jupiter (with R. T. Crawford), 266; Note on Comet c 1908 (with Sturla Einarsson) 266 Naval Observatory, Mare Island, Report of, 1907, by T. J. J. See 106 Nebula, Planetary, with Variable Nucleus 196 Nebulae, Discover>' of Many Small, Near Some of the Globular Star-Clusters, by C. D. Perrine 237 New Publications 50, 123, 199, 273, 298 Notes from Pacinc Coast Observatories . 27, 94, 181, 227, 264, 287 Notes from Science 45» I97» 242, 271, 296 Park hurst, H. M., Notice of Death of 122 Perrine, C. D., Progress on the Crossley Eros Solar Parallax Work, 184; Recent Observations of the Moving Object Near Jupiter, Discovered at Greenwich by Mr. J. Melotte, 184; Observations of the Partial Eclipse of the Sun June 28, 1908, 2ss; Discovery of Many Small Nebulae Near Some of the Globular Star-Clusters, 237; Some Results of a Study of the Structure of Photographic Films, 264; Photographic Defini- tion from Light of Different Wave-Lengths 292 Photographic Definition from Light of Different Wave-Lengths, by C. D. Perrine 292 Photographic Films, Some Results of a Study of the Structure of, by C. D. Perrine 264 Photographic Plate, A New, by E. A. Fath 239 Planetary Phenomena, by Malcolm McXkill .23,91,178.224,261, 284 Plummer, H. C, Lord Kelvin, 13; The Radial Velocity of aOrionis. 227; The Orbits of the Spectroscopic Binaries /S Hcrculis and 0 Lcoins 2.^ PoYNTiNc. J. 11., Some Astronomical Consequences of the Pres- sure of Light, Extract from an Article by 42 Pressure of Light, Some Astronomical Consequences of the, by J. H. PovxTiNd (extract) 42 Radial Velocity of aQrionis, by IL C. Plummer 227 Reports of Observatories for 1907 98, 186 Reseau, on the. by S. Albrecht 94 Riefler Clock, Xote on, by R. F. Saxford 29 Sanfori), R. ¥., Xote on Rietier Clock, 29; The Difference of Longitude between Lick Observatory and Mare Island Ob- servatory 2T^S Satunt's Rings, Observations of, in 1907, by R. G. Aitken* . . t^j See, T. J. J., Report of Xaval Observatory, Mare Island, 1907 . 106 Solar Vortices, by Gkor(]E E. Hale 203 Solar Vortices and the Zecman Effect, by George E. Hale . . 220 Solar Observatory, Report of the, of the Carnegie Institution of Washington for 1907, by George E. Hale 107 Astronomical Society of the Pacific, 307 PACE. Southern Observatory, Head of 47 Spectroscopic Binaries : Eighteen Stars Whose Radial Velocities Vary, by W. W. Campbeli 293 Methods of Determining the Orbits of Spectroscopic Binaries, by Heber D. Curtis 133 The Orbits of the Spectroscopic Binaries /3 Herculis and 0 Lcoiiis, by H. C. Plummer 2,V4 Spectra of the Limb and Center of the Sun, A Comparative Study of the, by George E. Hale and Walter S. Adams ... 27 Star-Stream in Taurus, A Remarkable, by W. W. Campbell 277 Struve, Hermann, Eclipses and Transits of the Satellites of Saturn Occurring in the Year 1908 156 Sun, The Zeeman Effect in the, by George E. Hale .... 287 Students' Observatory, University of California, Report of, 1907, by A. O. Leuschner 116 TowNLEY, Sidney D., Second Catalogue of Variable Stars, 41 ; Charles A. Young, 46; Vacation Pastimes 241 Vacation Pastimes, by S. D. Townley 241 Variable Stars, Second Catalogue of, by S. D. Townley ... 41 Variation of Latitude, The, by J. D. Maddrili 269 Young, Charles A., Notice of Death of, by S. D. Townley 46 Zodiacal Light, The Northern Limit of the, by E. A. Eath 280 M